9 The Son of God, therefore, having the charge of mankind, was first made man, that men might believe in Him; that He might be to us a witness, sprung from ourselves, of things Divine, and preach to us, weak and carnal as we are, through the weakness of the flesh concerning God the Father, so fulfilling the Father's will, even as He says, I came not to do My own will, but the will of Him that sent Me. It was not that He Himself was unwilling, but that He might manifest His obedience as the result of His Father's will, for His own will is to do His Father's.
This is that will to carry out the Father's will of which He testifies in the words: Father, the hour has come; glorify Your Son, that Your Son may glorify You; even as You have given Him power over all flesh, that whatsoever You have given Him, He should give it eternal life. And this is life eternal, that they should know You the only true God, and Him Whom You sent, Jesus Christ. I have glorified You upon earth, having accomplished the work which You gave Me to do. And now, O Father, glorify Me with Your own Self with the glory which I had with You before the world was.
I have manifested Your Name unto the men whom You have given Me</em>. In words short and few He has revealed the whole task to which He was appointed and assigned. Yet those words, short and few as they are, are the true faith's safeguard against every suggestion of the devil's cunning. Let us briefly consider the force of each separate phrase.
Source: On the Trinity (New Advent)