And Jesus cried out and said, “Whoever believes in me, believes not in me but in him who sent me. And whoever sees me sees him who sent me. I have come into the world as light, so that whoever believes in me may not remain in darkness. If anyone hears my words and does not keep them, I do not judge him; for I did not come to judge the world but to save the world. The one who rejects me and does not receive my words has a judge; the word that I have spoken will judge him on the last day. For I have not spoken on my own authority, but the Father who sent me has himself given me a commandment—what to say and what to speak. And I know that his commandment is eternal life. What I say, therefore, I say as the Father has told me.” —John 12:44-50
Concerning the unity of the Father and the Son, we must be content to believe reverently, what we cannot grasp mentally or explain distinctly. Let it suffice us to know that our Savior was not like the prophets and patriarchs, a man sent by God the Father, a friend of God, and a witness for God. He was something far higher and greater than this. He was in His Divine nature essentially one with the Father–and in seeing Him, men saw the Father who sent Him. This is a great mystery; but a truth of vast importance to our souls. He that casts His sins on Jesus Christ by faith is building on a rock. Believing on Christ, he believes not merely on Him, but on Him that sent Him.