John said:
Jesus did many other things as well. If every one of them were written down, I suppose that even the whole world would not have room for the books that would be written. (this appears to be an exaggeration, but the point is taken)
The NT is not the only record neither necessarily contains all that Jesus ever said or did. There were many other gospels back in the day, and more recent religious texts have attempted to express and preserve the sayings of Jesus as well,...see our thread on Gospel of Thomas
here
There is also the Gospel of the Holy 12 (or Nazareine Gospel), the Aquarian Gospel, Gnostic and Essene scriptures and others that contain sayings of Jesus, plus the UB, and some channeled works. Like everything, you weigh the content, meaning and value of the teachings and correlate them with all other facts and records, at last using your own intelligence, reason, logic and conscience, and spiritual discernment.