When you think about it, it is a logical question. Why didn’t Jesus write his own book? For that matter, why didn’t an angel hand the prophets a golden plate with prophecies written by the hand of God himself? (The Ten Commandments, after all, were written with the finger of God on tables of stone—God can write.)
There is no reason why Jesus could not have written his story, so we are left to ponder why he did not. There is a reason, and it turns out to be of profound importance in dealing with that collection of books we call the New Testament.
In the first place, biblical law places great importance on witnesses. Just as in our constitution, no man could be deprived of life, liberty, or property without due process of law. And that due process included witnesses to the cause of action against a man. No man could be deprived of his life for murder without at least two witnesses to the crime. Then there is a very practical reason why Jesus did not write his own book, and he stated it in his own words. We’ll find them in John, chapter 5.