Origen of Alexandria (On Prayer 10)

It remains, accordingly, to pray to God alone, the Father of All, not however apart from the High Priest who has been appointed by the Father with swearing of an oath, according to the words He hath sworn and shall not repent, "You art a priest forever after the order of Melchizedek." In thanksgiving to God, therefore, during their prayers, saints acknowledge His favors through Christ Jesus.

Just as the man who is scrupulous about prayer ought not to pray to one who himself prays but to the Father upon whom our Lord Jesus has taught us to call in our prayers, so we are not to offer any prayer to the Father apart from Him. He clearly sets this forth himself when He says, "Verily, verily, I tell you, whatsoever you may ask of my Father He shall give you in my house. Until but now you have not asked aught in my name. Ask and you shall receive, that your joy may be fulfilled."

He did not say, "Ask of me," nor yet simply "Ask of the father," but "Whatsoever you may ask of the Father, He will give you in my name." For until Jesus taught this, no one had asked of the Father in the name of the Son. True was the saying of Jesus, "Until but now you have not asked aught in my name"; and true also the words, "Ask and you shall receive, that your joy may be fulfilled." Should anyone, however who believes that prayer ought to be made to Christ himself, confused by the sense of the expression make obeisance, confront us with that acknowledged reference to Christ in Deuteronomy, "Let all God's angels make obeisance to Him," we may reply to him that the church, called Jerusalem by the prophet, is also said to have obeisance made to her by kings and queens who become her foster sires and nurses, in the words, "Behold, I lift up my hand upon the nations, and upon the isles will I lift up my sign: and they shall bring your sons in their bosom and your daughters they shall lift up on their shoulders; and kings shall be your foster sires, their queens they nurses: to the face of the earth shall they make obeisance to you, and the dust of your feet shall they lick: and you shall know that I am the Lord and shall not be ashamed."

And how does it not accord with Him who said, "Why callest you me good? None is good save One—God the Father" to suppose that He would say, "Why pray you to me? To the Father alone ought you to pray, to whom I also pray, as indeed you learn from the holy Scriptures. For you ought not to pray to one who has been appointed high priest for you by the Father and has received it from the Father to be advocate, but through a high priest and advocate able to sympathize with your weaknesses, having been tried in all points like you but, by reason of the Father's free gift to me, tried without sin.