The Bible does not contain the whole of Jesus’ teaching, or Christianity, as many Protestants believe

Mk 4:33 And with many such parables, he spoke to them the word, according as they were able to hear

Mk 6:34 And Jesus going out saw a great multitude: and he had compassion on them, because they were as sheep not having a shepherd, and he began to teach them many things.

Lk 24:15 And it came to pass, that while they talked and reasoned with themselves, Jesus himself also drawing near, went with them.
Lk 24:16 But their eyes were held, that they should not know him

Lk 24:25 Then he said to them: O foolish, and slow of heart to believe in all things, which the prophets have spoken.
Lk 24:26 Ought not Christ to have suffered these things, and so to enter into his glory?
Lk 24:27 And beginning at Moses and all the prophets, he expounded to them in all the scriptures, the things that were concerning him.

Jn 16:12 I have yet many things to say to you: but you cannot bear them now.

Jn 20:30 Many other signs also did Jesus in the sight of his disciples, which are not written in this book.

Jn 21:25 But there are also many other things which Jesus did; which, if they were written every one, the world itself, I think, would not be able to contain the books that should be written.

Acts 1:2 Until the day on which, giving commandments by the Holy Ghost to the apostles whom he had chosen, he was taken up.
Acts 1:3 To whom also he showed himself alive after his passion, by many proofs, for forty days appearing to them, and speaking of the kingdom of God.