John 14:9

So long time - For more than three years Jesus had been with them. He had raised the dead, cast out devils, healed the sick, done those things which no one could have done who had not come from God. In that time they had had full opportunity to learn his character and his mission from God. Nor was it needful, after so many proofs of his divine mission, that God should “visibly manifest” himself to them in order that they might be convinced that he came from him.

He that hath seen me - He that has seen my works, heard my doctrines, and understood my character. He that has given “proper attention” to the proofs that I have afforded that I came from God.

Hath seen the Father - The word “Father” in these passages seems to be used with reference to the divine nature, or to God represented “as a Father,” and not particularly to the distinction in the Trinity of Father and Son. The idea is that God, as God, or as a Father, had been manifested in the incarnation, the works, and the teachings of Christ, so that they who had seen and heard him might be said to have had a real view of God. When Jesus says, “hath seen the Father,” this cannot refer to the essence or substance of God, for He is invisible, and in that respect no man has seen God at any time. All that is meant when it is said that God is seen, is that some manifestation of him has been made, or some such exhibition as that we may learn his character, his will, and his plans. In this case it cannot mean that he that had seen Jesus with the bodily eyes had in the same sense seen God; but he that had been a witness of his miracles and of his transfiguration - that had heard his doctrines and studied his character - had had full evidence of his divine mission, and of the will and purpose of the Father in sending him. The knowledge of the Son was itself, of course, the knowledge of the Father. There was such an intimate union in their nature and design that he who understood the one understood also the other. See the notes at Matthew 11:27; also Luke 10:22; John 1:18.