Here after going back to former times, and looking back to God's original dispensation of things whereby the world has existed up to the present time, and having considered what special provision He had made for all occurrences, he is stricken with awe, and cries aloud, so making his hearers feel confident that certainly that will come to pass which he says. For he would not have cried aloud and been awe-struck, unless this was quite sure to come to pass. That it is a depth then, he knows: but how great, he knows not. For the language is that of a person wondering, not of one that knew the whole. But admiring and being awe-struck at the goodliness, so far forth as in him lay, he heralds it forth by two intensitive words, riches and depth, and then is awestruck at His having had both the will and the power to do all this, and by opposites effecting opposites. “How unsearchable are His judgments.” For they are not only impossible to be comprehended, but even to be searched. “And His ways past finding out;” that is, His dispensations for these also are not only impossible to be known, but even to be sought into. For even I, he means, have not found out the whole, but a little part, not all. For He alone knows His own clearly. Wherefore he proceeds:
<!--<span class="stiki"></span>-->Ver. 34, 35. “For who has known the mind of the Lord? Or who has been His counsellor? Or who has first given to Him, and it shall be recompensed unto him again?”
What he means is nearly this: that though He is so wise, yet He has not His Wisdom from any other, but is Himself the Fountain of good things. And though He has done so great things, and made us so great presents, yet it was not by borrowing from any other that He gave them, but by making them spring forth from Himself; nor as owing any a return for having received from him, but as always being Himself the first to do the benefits; for this is a chief mark of riches, to overflow abundantly, and yet need no aid. Wherefore he proceeds to say, “For of Him, and through Him, and to Him, are all things.” Himself devised, Himself created, Himself works together (Vulg. συγκρατεἵ, manuscripts συγκροτεἵ). For He is rich, and needs not to receive from another. And wise, and needs no counsellor. Why speak I of a counsellor? To know the things of Him is no one able, save Himself alone, the Rich and Wise One. For it is proof of much riches that He should make them of the Gentiles thus well supplied; and of much wisdom that He should constitute the inferiors of the Jews their teachers. Then as he was awe-struck he offers up thanksgiving also in the word, “To Whom be glory forever. Amen.”
For when he tells of any great and unutterable thing of this kind, he ends in wonder with a doxology. And this he does in regard to the Son also. For in that passage also he went on to the very same thing that he does here. Of whom is Christ according to the flesh, Who is over all God blessed forever. Amen.
Source: Homilies on Romans (New Advent)