Jesus may have sometimes said something like, “It is written...”.
But mostly he would say, “At a Council in 600 BC, 63% of attending clerics voted for “B” and we’ve accepted “B” ever since...”
Funny... However, if Jesus said “it is written”. He was necessarily referring to the Old Teatament, as it was the only Scripture at the time. In all seriousness, I don’t understand the logic of saying the bible is the be all and end all... When it never says that, nor did Jesus. He did however, pass on many things that were not recorded in the gospels.