10 Thus much then at present, in the way of a digression, to put you in remembrance. Let me, however, add yet another testimony in proof that God is called the Father of men in an improper sense. For when in Esaias God is addressed thus, For You are our Father, though Abraham be ignorant of us, and Sarah travailed not with us, need we inquire further on this point? And if the Psalmist says, Let them be troubled from His countenance, the Father of the fatherless, and Judge of the widows, is it not manifest to all, that when God is called the Father of orphans who have lately lost their own fathers, He is so named not as begetting them of Himself, but as caring for them and shielding them. But whereas God, as we have said, is in an improper sense the Father of men, of Christ alone He is the Father by nature, not by adoption: and the Father of men in time, but of Christ before all time, as He says, And now, O Father, glorify Thou Me with Your own self, with the glory which I had with You before the world was.
Source: Catechetical Lectures (New Advent)