What does John 6:45-47 mean?

45 It is written in the prophets, And they shall be all taught of God. Every man therefore that hath heard, and hath learned of the Father, cometh unto me. 46 Not that any man hath seen the Father, save he which is of God, he hath seen the Father. 47 Verily, verily, I say unto you, He that believeth on me hath everlasting life. (John 6:45-47 KJV)

William Burkitt’s Commentary

In these words our blessed Saviour confirms his former assertion, concerning his Father’s drawing, from the prophecies of the Old Testament, which, speaking of the days of the Messias, foretold, that persons should be taught of God to embrace the Messias; whence Christ inferreth, that every one who is thus taught, shall come upon him, and believe in him.

Learn hence, 1. That the teachings of God are absolutely necessary to every man that cometh unto Christ in the way of faith, 2. That such shall not miscarry in the way of faith, who are under the special teachings and instructions of God; They shall be all taught of God, and he teacheth to profit, and that not only authoritatively, but efficaciously and effectually. Those whom God undertakes to teach, receive from him both an ear to hear, and an heart to understand. They shall be all taught of God, and they that are taught, have heard and learned of the Father.