‘Jesus therefore answered them and said, “My teaching is not mine, but His that sent me. If any man really wants to do His will, he will know of the teaching, whether it be of God, or whether I speak of myself”.'
Jesus answered their amazement and explained the source of His teaching. ‘My teaching is not mine, but His Who sent me. If any man's will is to do His will, he will know whether the teaching is from God or whether I am speaking on my own authority'. He wanted them to know that it was God who had taught Him, with the result was that His teaching was such that those who really wanted to know and do God's will would recognise it for what it was. If they were really of God therefore they would recognise that what He spoke was of God. He stressed that He did not speak on His own authority, but on God's, and that His teaching was such that, to those who judged fairly, it revealed God's truth. So if they wanted to understand Him and know the truth let them set their hearts right towards God, and then they would genuinely know the truth of what He was saying.
Knowing that the Scribes and Pharisees would never enunciate teaching without quoting the authority of earlier teachers, and that this was what the crowds would expected, Jesus therefore quoted His authority. It was God Who was His authority.
It is significant that while in John's Gospel Jesus constantly spoke in such a way as to point to His teaching as evidence of His Sonship, comparatively little of that teaching has until now been given to us in the Gospel (apart from in chapter 5). It is quite clear therefore that John is expecting his readers to have read or heard that teaching elsewhere. He assumes a wide knowledge of it. And while it was, of course, true that there was the oral tradition, those who had known Jesus had almost all died out. Thus it can be assumed that the writer was depending on the other Gospels (which he would know about) and the tradition in the churches, as having given the details of Jesus' teaching necessary to back up His claims. But in view of the fact that there is no evidence in the Gospel of words borrowed from the other Gospels it is doubtful whether he had copies of those Gospels available to him
‘Whether I speak of myself'. Whether the source of His ideas came just from His own head, or whether they came from God.