"And the Jews marvelled, saying, How knoweth this man letters, having never learned?" (John 7:15)
In the midst of the annual feast of tabernacles, "Jesus went up into the temple, and taught" (John 7:14), and the unique caliber of His teaching (literally "indoctrinating") caused the Jewish scholars there to "marvel."
Their question on this occasion was how an uneducated man, who had never been taught by the scribes and rabbis, could have acquired such a remarkable understanding of the Holy Scriptures. He had never had formal training in the Word; yet, when He taught, "He taught them as one having authority, and not as the scribes" (Matthew 7:29).
His answer to their question was amazing: "My doctrine |or 'teaching'| is not mine, but his that sent me" (John 7:16).
There are two factors at work here. First of all, His working knowledge of the Old Testament Scriptures was encyclopedic, acquired in the same way any other student of the Word can acquire it--by diligent and prayerful personal study thereof. He had done this all His life from the time He was a small boy. Remember how He had "asked questions" of the astonished doctors in the temple, and then how He was "subject unto" His parents, and how He "increased in wisdom and stature, and in favour with God and man" (Luke 2:46, 51-52). In all of this, He is a perfect human example to us, as we also seek to learn the Scriptures and to grow in wisdom and in favor with God.
But beyond His human understanding of the Word, of course, was His own innate divine wisdom and authority. He was eternal God, as well as perfect man. Thus He not only has authenticated the former Scriptures and given us an example in their study and use, but has also conveyed perfectly to us, through His holy apostles and prophets, the Scriptures of the New Covenant as well. HMM