Albert Barnes Commentary John 14:9

"Jesus saith unto him, Have I been so long time with you, and dost thou not know me, Philip? he that hath seen me hath seen the Father; how sayest thou, Show us the Father?" — John 14:9 (ASV)

So long time. For more than three years Jesus had been with them. He had raised the dead, cast out demons, healed the sick, and 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 necessary, after so many proofs of his divine mission, that God should visibly manifest himself to them so that they might be convinced that he came from him.

He that hath seen me. He who has seen my works, heard my doctrines, and understood my character. He who has given proper attention to the proofs that I have given 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 those 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 so that we may learn his character, his will, and his plans.

In this case it cannot mean that he who had seen Jesus with the bodily eyes had in the same sense seen God; but he who had been a witness of his miracles and of his transfiguration—who 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 Barnes on Matthew 11:27)

(See Barnes on Luke 10:22; See Barnes on John 1:18).