2 Timothy 3: 16
All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, ... NIV
It is imagined that by the second century CE there was a movement in the early church to establish which books available within the church could be considered to be authoritative.
It seems that the document called the Muratorian fragment is one of the earliest extant attempts to provide such a list. Its called a fragment because the introduction is missing, and it starts (as you see below) in the middle of a sentence.
Found in the 18th century CE by an Italian scholar named Muratori, the date of the original is disputed, but many think it belongs to the later second century CE (i.e. between 150 to 190 CE ).
So, for at least one hundred plus years after Jesus, there was no NT, as we know it.
The document lists 22 of the 27 NT books now recognised by the church. It does not list Hebrews, James, 1 and 2 Peter and 3 John. It also includes The Wisdom of Solomon and the Apocalypse of Peter. The then popular Shepherd of Hermas is accepted conditionally. That is, it could be read in church, but was not held to be a sacred text.