John Chrysostom

"What if God, willing to show His wrath, and to make His power known, endured with much long-suffering the vessels of wrath fitted to destruction: and that He might make known the riches of His glory on the vessels of mercy, which He had afore prepared unto glory, even us, whom He hath chosen, not of the Jews only, but also of the Gentiles." What he means is somewhat as follows. Pharaoh was a vessel of wrath, that is, a man who by his own hard-heartedness had kindled the wrath of God. …

Homily on Romans 16 ↗

Theophylact of Ohrid

Having shut the mouth of the curious, he now gives the solution. The meaning of what is said is as follows. Pharaoh was a vessel of wrath, that is, a man who by his hardheartedness kindles the wrath of God. God "endured" him, that is, bore with him, was patient; for He deemed him worthy of great longsuffering. …

Commentary on Romans ↗

Thomas Aquinas

Then, when he says what if God, willing, he answers the first question, namely, why God wills to be merciful to some and leave others in wretchedness, i.e., to choose some and reject others. Here it should be noted that the end of all divine works is the manifestation of divine goodness: the Lord has made all things for himself (Prov 16:4). Hence, it was stated above that the invisible things of God have been clearly perceived in the things that have been made (Rom 1:20). …

Commentary on Romans ↗