R.V.G Tasker Professor of New Testament Exegesis at the University of London remarks that;
“There were at least thirty five years of Christian teaching and Christian missionary activity before the believers were in possession of the written records of Christ’s life and teaching, which we know as the four Gospels”…
“Our faith today is bound to be conditioned by the four Gospels. The faith of the earliest Christians was independent of them.”
Even today a lot of emphasis is placed on the time that transpired between the “verbal” teaching of the Apostles and the “written” narrative of the Life and teaching of Jesus Christ.
“The earliest Christians concerned themselves with the instruction of Jesus to herald the gospel to all (Matt.28:19, Acts 1:8) and did not waver to do this effectively with the reality of persecution (Act8). “What was paramount in the apostles’ earliest motives was oral proclamation of the gospel.”
We can clearly see that the early Church spread the news orally and did not bother at first to do so in written form. The reason that they did seem keen to do so later was:
“First the Apostles started to die off. And second, the Lord’s return was evidently not going to happen within the first few decades of the church’s existence”.
It is important to note that at the very construction of the four Gospels and the Epistles some of the original Apostles were still alive and never raised concern about the central message displayed within them and confirmed the message (evangelion) as revealed in them to be legitimate (Joh.21:24,2 Pet. 3:15,16). The central claim of the four Gospels is fundamentally the expressed realized message as recognized in the whole of the Christian Canon.
FF Bruce writes
“The Gospel, that is to say, is contained in the canon, but is not coextensive with the canon. The canon, to adapt Luther’s metaphor, is the cradle in which the gospel is laid”. 
We can recognize that when the authors speak and write they do so in anticipation of the “Old” [testament] being revealed in the “New” [Gospels and Epistles]: They allude to the fact that:
“Now all this took place to fulfill what was spoken by the Lord through the prophet” (Matt 1:22-23).
The earliest written sources was therefore concerned with the actual fulfillment of the Old Testament promise (Matt.2:15,23,5:17,8:17,12:17,13:35,21; Luke 21:22,24:44, John 10:35,12:38-40,15:25,17:12,18:9,19:36,37,Acts3:18, 13:27-29, Rev.17:17).
The way the Early Christians interpreted the coming of Jesus Christ was foundationally directly related to what was prophetically foretold in the Old Testament Scriptures. The author of Hebrews writes:
“Long ago God spoke to the fathers by the prophets at different times and in different ways. In these last days, He has spoken to us by His Son” (Heb.1:1-2).
The Gospels in essence then captivated the essential message of Christ. Mark therefore writes:
“The beginning of the gospel of Jesus Christ, the Son of God. 2 As it is written in Isaiah the prophet” (Mark 1:1-2)
He also adds:
“Jesus went to Galilee, preaching the good news [Evangelion] of God: “The time is fulfilled, and the kingdom of God has come near. Repent and believe in the good news [Evangelion]!” (V/14-15).
Now Mark identifies Jesus speaking of three different realities when He announced the Gospel message:
§ The “Proto-Evangelion” [fulfillment requires the previous prediction and this is found early in Scripture in the proto-evangelion].
§ The “Evangelion” [this is displayed in the central understanding and teaching of the earliest Christians and could be identified as the earliest confession and profession of faith].
§ Kerygma [this is simply the declaration of salvation] and its influence on the Rule of Faith [Regula fidei: This is the common understanding of the core tenets early Christian message] followed by the Earliest Christians.
The earliest reality in the Judeo/Christian narrative is the reality of God, the creation of everything including a man in the “imago dei” as well as the subsequent fall of man (Gen.1-3) The central idea of the Judeo/Christian expectation, therefore, is found in Genesis 3:15 where God says: “I will put enmity between you and the woman, and between your seed and her Seed”. The very central theme for the rest of the Canon of Scripture occupies itself with the coming of the Messiah and the ultimate salvation of man. This reference in Scripture is known as the “proto” (Greek prefix) or “first” euangelion or “gospel”.
Theologian Dr. Ray Pritchard writes
“This is the first promise given after Adam and Eve ate the forbidden fruit in the Garden of Eden. Theologians call it the protoevangelium–or first gospel because these words spoken by God contain the first promise of redemption in the Bible. Everything else in the Bible flows from these words in Genesis 3:15.”
As the acorn contains the mighty oak, so these words contain the entire plan of salvation. The great English preacher Charles Simeon called this verse “the sum and summary of the whole Bible.” Christ was understood by early Christians to be the ultimate “seed” of the woman who would crush the serpent’s head (Rom.16:20, Rev.12:17). This verse foretells Jesus’s victory over Satan yet His own wounding in the process. Christ’s was the one who came as a fulfillment of this promise caused by Adam’s sin which is fully realized as Christ in His great sacrifice redeem mankind through His willful sacrifice by which we were made free.
The earliest Christians understood the Scriptures to be the unfolding narrative that found its ultimate conclusion in the person, work and mission of Jesus Christ. The Gospel authors clearly endeavored to show how the prophets of Old predicted what they have seen and heard about Jesus Christ (i.e. Matt.1:22-23; 2:6 &18; 3:3, 4:14-16, 8:14-17; Acts1:20-26, 2:16-37). Paul understands that the enigmatic story of the Gospels “having been built on the foundation of the apostles and prophets, Christ Jesus Himself being the cornerstone” (Eph.2:20).
Professor R.V.G Tasker recognizes an early idea that influenced the “Paradosis” or teaching of the earliest Christians and affirms that in the Epistles and the book of Acts we can recognize “what was proclaimed as the gospel”. He added:
“to quote from the Epistle to the Romans – the good news that what God had promised by His prophets in the Holy Scriptures (i.e. the Old Testament) concerning a blessed age to be inaugurated by God’s anointed messenger, or Christ, had been fulfilled in Jesus. The resurrection of Jesus from the dead was the divine guarantee that such a fulfillment had taken place…. The central point of the gospel, on which everything depended, was the resurrection”.
The early Church before the actual written accounts of the four Gospels understood the earliest message of Christ and the expectation of the Old Testament Scriptures. The “Good News” is therefore clearly summed up and as Scholar C.H Dodd notes it is taught by the Apostle Peter in the book of Acts (Acts 2:14-41; Acts 3:11-4:4; Acts 10:34-43).
The central “Gospel” message [Evangelion] is therefore seen as:
“1. The Age of Fulfillment has dawned, the “latter days” foretold by the prophets. Acts 3:18-26
2. This has taken place through the birth, life, ministry, death and resurrection of Jesus Christ. Acts 2:22-31
3. By virtue of the resurrection, Jesus has been exalted at the right hand of God as Messianic head of the new Israel. Acts 2:32-36
4. The Holy Spirit in the church is the sign of Christ’s present power and glory. Acts 10:44-48
5. The Messianic Age will reach its consummation in the return of Christ. Acts 3:20-21
6. An appeal is made for repentance with the offer of forgiveness, the Holy Spirit, and salvation. Acts 2:37-41” 
We have come full circle now in that we can recognize clearly that the earliest proclamation (Kerygma) was clearly evident in the teaching of the first Christians. On the nature of the “Kerygma” Herman N. Ridderbos writes “Kerygma, the proclamation and the declaration of salvation… is the most typical designation of the character of the content of the New Testament, at least with respect to the primary meaning and significance of that content. The noun kerygma is used relatively infrequently to describe the character and content of New Testament revelation”… The proclamation or Gospel (Evangelion) of the earliest Christians is then unanimously attested as being “used in a way that is very close in meaning to “kerygma” and “kerussein” (e.g. Mark13:10, 14:9, 16:15, Gal 2:2; Col.1:23; Matt.26:13, 24:14ff).
Ridderbos shows that;
“When used to describe the New Testament revelation, kerygma and kerussein derive their central meaning directly from the content of the New Testament revelation itself.”
Above all, that content consists of a new and decisive event, the coming of the kingdom of God the dawn of a great time of salvation that God had promised and His people had long awaited. Thus the content of the kerygma is variously described as the kingdom of God (Luke8:1, 9:2; Acts28:31), as the acceptable year of the Lord (Luke 4:19), as Christ (Acts 8:5, Phil.1:15), and as the baptism of repentance for the remission of sins (Mark 1:4, 3:3), all of which describe God’s acts of fulfillment and consummation in the coming and work of Christ”. There was no other revelation evident within history and early Christian Society that contradicted this reality.
“As the proclamation of salvation, the kerygma in its original form is found most clearly in the Gospels, which according to Mark contain “the Gospel of Jesus Christ” (1:1), that is, the apostolic proclamation about the advent of the great era of redemption (cf. Luke 1:1-4)”.
Therefore the Pauline Kerygma is evident and as C.H. Dodd holds:
“It is true that the kerygma as we have recovered it from the Pauline epistles is fragmentary. No complete statement of it is, in the nature of the case, available. But we may restore it in outline somewhat after this fashion: The prophecies are fulfilled, and the new Age is inaugurated by the coming of Christ. He was born of the seed of David. He died according to the Scriptures, to deliver us out of the present evil age. He was buried. He rose on the third day according to the Scriptures. He is exalted at the right hand of God, as Son of God and Lord of quick and dead. He will come again as Judge and Saviour of men.”
The Earliest Historical and Biblical outline for the Kerygma is as follow:
· The promises of God made in the OT have now been fulfilled with the coming of Jesus the Messiah (Book of Acts 2:30; 3:19, 24, 10:43; 26:6-7, 22; Epistle to the Romans 1:2-4; 1 Timothy 3:16; Epistle to the Hebrews 1:1-2; 1 Peter 1:10-12; 2 Peter 1:18-19).
· Jesus was anointed by God at his baptism as Messiah (Acts 10:38).
· Jesus began his ministry in Galilee after his baptism (Acts 10:37).
· He conducted a beneficent ministry, doing good and performing mighty works by the power of God (Mk 10:45; Acts 2:22; 10:38).
· The Messiah was crucified according to the purpose of God (Mk 10:45; Jn 3:16; Acts 2:23; 3:13-15, 18; 4:11; 10:39; 26:23; Ro 8:34; 1 Corinthians 1:17-18; 15:3; Galatians 1:4; Heb 1:3; 1Peter 1:2, 19; 3:18; 1 Jn 4:10).
· He was raised from the dead and appeared to his disciples (Acts 2:24, 31-32; 3:15, 26; 10:40-41; 17:31; 26:23; Ro 8:34; 10:9; 1Co 15:4-7, 12ff.; 1 Thessalonians 1:10; 1Tim 3:16; 1Peter 1:2, 21; 3:18, 21).
· Jesus was exalted by God and given the name “Lord” (Acts 2:25-29, 33-36; 3:13; 10:36; Rom 8:34; 10:9; 1Tim 3:16; Heb 1:3; 1Peter 3:22).
· He gave the Holy Spirit to form the new community of God (Ac 1:8; 2:14-18, 33, 38-39; 10:44-47; 1Peter 1:12).
· He will come again for judgment and the restoration of all things (Ac 3:20-21; 10:42; 17:31; 1Co 15:20-28; 1Th 1:10).
· All who hear the message should repent and be baptized (Ac 2:21, 38; 3:19; 10:43, 47-48; 17:30; 26:20; Ro 1:17; 10:9; 1Pe 3:21).
“As the Church produced a settled organization of its life, the content of the kerygma entered into the Rule of Faith, which is recognized by the theologians of the second and third centuries as the presupposition of Christian theology. Out of the Rule of Faith, in turn, the Creeds emerged. The so-called Apostles’ Creed in particular still betrays in its form and language its direct descent from the primitive apostolic Preaching”.
F F Bruce writes on the rule of faith that:
“If at times [the rule of faith] is formally distinguished from Scripture in the sense that it is recognized as the interpretation of Scripture, at other times it is materially identical with Scripture in the sense that it sums up what Scripture says.”
Rule of Faith as expressed by the early Church Fathers
Irenaeus of Lyons (130A.D-202A.D) writes;
“Since therefore we have such proofs, it is not necessary to seek the truth among others which it is easy to obtain from the Church; since the apostles, like a rich man [depositing his money] in a bank, lodged in her hands most copiously all things pertaining to the truth: so that every man, whosoever will, can draw from her the water of life. For she is the entrance to life; all others are thieves and robbers. On this account are we bound to avoid them, but to make choice of the thing pertaining to the Church with the utmost diligence, and to lay hold of the tradition of the truth. For how stands the case? Suppose there arise a dispute relative to some important question among us, should we not have recourse to the most ancient Churches with which the apostles held constant intercourse, and learn from them what is certain and clear in regard to the present question? For how should it be if the apostles themselves had not left us writings? Would it not be necessary, [in that case,] to follow the course of the tradition which they handed down to those to whom they did commit the Churches?”
“To which course many nations of those barbarians who believe in Christ do assent, having salvation written in their hearts by the Spirit, without paper or ink, and, carefully preserving the ancient tradition, believing in one God, the Creator of heaven and earth, and all things therein, by means of Christ Jesus, the Son of God; who, because of His surpassing love towards His creation, condescended to be born of the virgin, He Himself uniting man through Himself to God, and having suffered under Pontius Pilate, and rising again, and having been received up in splendor, shall come in glory, the Saviour of those who are saved, and the Judge of those who are judged, and sending into eternal fire those who transform the truth, and despise His Father and His advent. Those who, in the absence of written documents, have believed this faith, are barbarians, so far as regards our language; but as regards doctrine, manner, and tenor of life, they are, because of faith, very wise indeed; and they do please God, ordering their conversation in all righteousness, chastity, and wisdom. If anyone were to preach to these men the inventions of the heretics, speaking to them in their own language, they would at once stop their ears, and flee as far off as possible, not enduring even to listen to the blasphemous address. Thus, by means of that ancient tradition of the apostles, they do not suffer their mind to conceive anything of the [doctrines suggested by the] portentous language of these teachers, among whom neither Church nor doctrine has ever been established.” 
“Now, with regard to this rule of faith-that we may from this point acknowledge what it is which we defend-it is, you must know, that which prescribes the belief that there is one only God, and that He is none other than the Creator of the world, who produced all things out of nothing through His own Word, first of all sent forth; that this Word is called His Son, and, under the name of God, was seen “in diverse manners” by the patriarchs, heard at all times in the prophets, at last brought down by the Spirit and Power of the Father into the Virgin Mary, was made flesh in her womb, and, being born of her, went forth as Jesus Christ; thenceforth He preached the new law and the new promise of the kingdom of heaven, worked miracles; having been crucified, He rose again the third day; (then) having ascended into the heavens, He sat at the right hand of the Father; sent instead of Himself the Power of the Holy Ghost to lead such as believe; will come with glory to take the saints to the enjoyment of everlasting life and of the heavenly promises, and to condemn the wicked to everlasting fire, after the resurrection of both these classes shall have happened, together with the restoration of their flesh. This rule, as it will be proved, was taught by Christ, and raises amongst ourselves no other questions than those which heresies introduce, and which make men heretics.”
Clement of Alexandria (150 A.D.-215 A.D.) said:
“Therefore in substance and idea, in origin, in pre-eminence, we say that the ancient and universal Church is alone, collecting as it does into the unity of the one faith-which results from the peculiar Testaments, or rather the one Testament in different times by the will of the one God, through one Lord-those already ordained, whom God predestinated, knowing before the foundation of the world that they would be righteous. But the pre-eminence of the Church, as the principle of union, is, in its oneness, in this surpassing all things else, and having nothing like or equal to itself. But of this afterwards.” 
 Tasker R.V.G. The Nature and purpose of the Gospels. Pg.9.
 Reinventing Jesus Pg.26.
 Reinventing Jesus Pg.27.
 The Canon of Scripture. Pg. 272-273.
 Tasker R.V.G. The Nature and purpose of the Gospels. Pg.10-11.
 The Apostolic Preaching and Its Developments by C. H. Dodd: Chapter One: The Primitive Preaching Pg11-13
 Redemptive history and the New Testament Scriptures by Herman N. Ridderbos Pg.50-52).
 The Apostolic Preaching and Its Developments by C. H. Dodd: Chapter One: The Primitive Preaching Pg9.
 The Apostolic Preaching and Its Developments by C. H. Dodd: Chapter One: The Primitive Preaching Pg.43.
 The Canon of Scripture, 1988, Pg. 117
 Against Heresies, book 3, 4, 1-2.
 The Prescription Against Heretics, Chapter XIII.
 Book 7, Ch 17, The Tradition of the Church Prior to that of the Heresies.