Sometimes our viewpoint of the first century church is badly skewed by our Bible-centric approach to faith. We don't intuitively understand how the first generations of church functioned without what we consider to be an essential component of Christian belief. In essence, we need to understand why we have a New Testament at all: the reason these texts were preserved was in order to preserve the original apostolic teaching as received by the early church.
The New Testament did not exist as a recognised single set of texts for the original generation of believers, and was never promised or idealised as some kind of essential component of our faith. This is a key difference between the legacies of Jesus and Mohammed - Mohammed wrote a book, but Jesus trained Disciples. As was once observed by C S Lewis, "[God] seems to do nothing of himself which He can possibly delegate to His creatures."
What Was The Faith once Delivered?
The first generation did have one clear thing in common - each was established by one of the Apostles, or another leader closely linked with them. Jesus had trained up specific individuals who were sent to establish churches:
"you will receive power when the Holy Spirit comes on you; and you
will be my witnesses in Jerusalem, and in all Judea and Samaria, and
to the ends of the earth." (Acts 1:8)
During the early centuries of the church, there were diverging approaches to faith - some more Greek, some more Jewish, and others of Gnostic or other strands. When Jude talks about the 'faith once delivered', he's seeking to turn the people back to the original teaching received by the Apostles who founded their churches, and not to the newer variations of faith. This is borne out several times in the text:
"For certain individuals whose condemnation was written about long
ago have secretly slipped in among you. They are ungodly people, who
pervert the grace of our God into a license for immorality and deny
Jesus Christ our only Sovereign and Lord." (Jude 1:4)
Jude highlights that the current wave of teaching he is addressing is one which:
- Emphasises grace to the expense of morality and holiness (v4 / v19)
- Denies Jesus Christ as δεσπότης (master/sovereign) and Lord (v4)
- Discards the original leadership and teaching of the church (v8)
In his response, he points them back to the teaching of the Apostles - persevering in prayer, building one another up in faith and remaining in the love and mercy of God and of the Lord Jesus:
"But, dear friends, remember what the apostles of our Lord Jesus Christ foretold.
They said to you, “In the last times there will be
scoffers who will follow their own ungodly desires.” These are the
people who divide you, who follow mere natural instincts and do not
have the Spirit. But you, dear friends, by building yourselves up in your most holy
faith and praying in the Holy Spirit, keep yourselves in God’s love as
you wait for the mercy of our Lord Jesus Christ to bring you to
eternal life." (Jude 1:17-20)
How was it delivered?
"Christ himself gave the apostles, the prophets, the evangelists, the
pastors and teachers, to equip his people for works of service, so
that the body of Christ may be built up until we all reach unity in
the faith and in the knowledge of the Son of God and become mature,
attaining to the whole measure of the fullness of Christ." (Ephesians
4:11-13)
Paul lays out the ordering of authority commonly understood by the early church - their doctrine was first of all founded on the teaching of the first generation of Apostles. Secondly, they were firmly rooted in the Old Testament, commonly referred to by early Christians as the Prophets. Thirdly, they had their own human teachers - Evangelists, pastors and teachers. As the second century progressed, 'Evangelist' soon became a recognised term for the Gospel accounts, and so these first three in Paul's list were typically understood to be a summation of the NT Letters, OT Texts and the NT Gospels, and then the latter two were the earthly teachers within their own church contexts.
The Apostolic Fathers writing in the second century (notably Clement of Rome & Ignatius) repeatedly called churches to return to obedience to the elders appointed by the Apostles and those approved by them, and so even before the NT was canonised the general thrust of church history is all about adhering to the original teaching and authority set forth by the Apostles and those they had approved/appointed to lead the church.
And so by these collective sources coupled with the living witness of the Holy Spirit, the entire church was admonished to carry on the true Apostolic tradition delivered by Christ through the Apostles to the church. The Apostles, together with all that they taught, including the preserved teaching of Christ was this 'true faith' once delivered for which the early church contended. There was no contemporary expectation of continuing 'apostleship' in the church beyond this first generation, and so this was considered a one-time event.
The 'delivery' of the faith was not a brief moment, but an extended duration encompassing the Apostles' time on earth. As "Apostles" (messengers/envoys) their very ministry was the delivery of the faith to the first churches. And so the accurate preservation and adherence to their teaching was the key concern.
Appendix A: If early Christians didn't have complete Bibles, what was their source of authority?
As not all churches had access to written accounts of Apostolic writings (and much of the church was illiterate) oral tradition had a very large but difficult to measure place to play in their understanding. The Apostles' teaching was ultimately formalised in the NT Letters, but for a long time was also maintained through oral traditions and secondary documents such as the Didache. By comparing the Didache with Jesus' teaching in Matthew 5-7, we can perhaps understand for ourselves how this first generation 'oral teaching' was often a reformulation of words and phrases handed down from the Apostles to the early church, codified into bite-sized units that could be memorised and passed on from disciple to disciple.
In part this contributed to the fracturing of agreed doctrine between churches, as churches in each region had access to slightly different sets of texts and different received traditions, and were subject to the leadership of their own leaders who might have had their own perspectives on matters. Today we understand the codification of the New Testament to be part of that effort to formalise across all churches which letters they understood to bear that original, authentic Apostolic authority - and therefore a common standard for how all churches were to pursue and adhere to the original received teachings as set forth by Christ to his Apostles.
Appendix B: Would Jude perceive disparity between the teaching of the Twelve and Paul?
Some modern scholarship influenced by the legacy of the Reformation tends to portray a big divide between Paul and the other Apostles, but based on the NT accounts of their interactions and later witnesses there's no contemporary mention of the two being in conflict. I would point to Acts 15:1-15 and 2 Peter as key evidence for this:
Bear in mind that our Lord’s patience means salvation, just as our
dear brother Paul also wrote you with the wisdom that God gave him. 16
He writes the same way in all his letters, speaking in them of these
matters. His letters contain some things that are hard to understand,
which ignorant and unstable people distort, as they do the other
Scriptures, to their own destruction. (2 Peter 3:16)
As far as we can tell, Jude and the rest of the early church fathers saw the 'Apostolic generation' as being in one accord when it came to the core teaching of 'the faith'. The "once delivered" aspect does not just refer to the literal written and spoken material delivered by Jesus to the Apostles, but also the Apostles and teachers they appointed themselves as being key sources of truth. The Faith once delivered to the saints was one which held all the Apostles and their appointed representatives as authoritative sources of truth.
Jude's view of faith (as well as Paul's, incidentally) assumes unity and conformance throughout the church, its people and its teachings. On the other hand, the false teachers he targets are those whom sow discord by setting up teachings and teachers against one another, trying to fracture the church by pitting God's words against one another:
"In the very same way, on the strength of their dreams these ungodly people pollute their own bodies, reject authority and heap abuse on celestial beings." (Jude 1:8)
Again, Clement of Rome and Ignatius' letters in the second century expounded these themes more fully not too long afterwards.