Chapter 6.
83 Rightly then is the woman checked, who demanded what was impossible, as a special kind of privilege from Him the Lord, Who of His own free gift granted not only to two apostles, but to all the disciples, those things which He had adjudged to be given to the saints; and that too without a prayer from any one, as it is written: “You shall sit upon twelve thrones, judging the twelve tribes of Israel.”
84. Therefore, although we may think the demand to have been possible, there is no room for false attacks. However, when I read that the seraphim stand, how can I suppose that men may sit on the right hand or the left of the Son of God? The Lord sits upon the cherubim, as it says: “You that sits upon the cherubim, show myself.” And how shall the apostles sit upon the cherubim?
85. And I do not come to this conclusion of my own mind, but because of the utterances of our Lord's own mouth. For the Lord Himself later on, in commending the apostles to the Father, says: “Father, I will that they also whom You have given Me be with Me where I am.” But if He had thought that the Father would give the divine throne to men, He would have said: “I will that where I sit, they also may sit with Me.” But He says: “I will that they be with Me,” not “that they may sit with Me;” and “where I am,” not “as I am.”
86. Then follow the words: “That they may see My glory.” Here too He did not say: “that they may have My glory,” but “that they may see” it. For the servant sees, the Lord possesses; as David also has taught us, saying: “That I may see the delight of the Lord.” And the Lord Himself in the Gospel has revealed it, stating: “Blessed are the pure in heart, for they shall see God.” “They shall see,” He says; not “They shall sit with God upon the cherubim.”
87. Let them therefore cease to think little of the Son of God according to His Godhead, lest they should think little also of the Father. For he who believes wrongly of the Son cannot think rightly of the Father; he who thinks wrongly of the Spirit cannot think rightly of the Son. For where there is one dignity, one glory, one love, one majesty, whatsoever you think is to be withdrawn in the case of any one of the Three Persons, is withdrawn from all alike. For that can never have completeness which you can separate and divide into various portions.
Source: On the Christian Faith (De fide) (New Advent)