The Church teaches that Christ instructed his disciples and they carried on his teachings, leaving a rough framework for a working church, but the teachings aren't in scripture. Our Protestant brothers are inclined to think Catholic practices evolved over the centuries, but that's not the Catholic way of thinking.
It's striking how many times the Gospels merely say that Jesus taught in the synagogues, proclaimed the gospel of the kingdom, and such . . . without saying what he actually said, plus the references to teaching the disciples things in private and the concluding remarks of John (“There are many other things that Jesus did, but if these were to be described individually, I do not think the whole world would contain the books that would be written”).
The Church teaches that those repeated laconic references throughout the Gospels to his teaching means he said a lot more than just what the Gospels record. He wasn't a stand-up comedian with a schtick that he repeated over and over again.
