John Chrysostom

Yet surely it is no where written in the Law, but as I said before, he calls always the whole of the Old Testament, the Law: both the prophets and the historical books And he brings forward his testimony from Esaias the prophet, again covertly detracting from the glory of the gift, for their profit; nevertheless, even thus he states it with praise. For the expression, "not even thus," hath force to point out that the miracle was enough to astonish them; and if they did not believe, the fault was theirs. …

Homily on 1 Corinthians 36 ↗

Theophylact of Ohrid

Again he compares prophecy with tongues and shows the superiority of the former, and wherein it consists is evident from what is said further. By "the Law" he customarily means the entire Old Testament. Therefore now too he says that the words written at the end of the book of Isaiah (Isa. 28:11–12) are written in the Law. By the words "but even then they will not listen to Me" he shows that the miracle could astonish them, but if they were not persuaded, the fault is theirs. …

Commentary on 1 Corinthians ↗

Thomas Aquinas

Then when he says: it is written in the law, he argues to his proposition. Here it should be noted that this argument, as is clear from a Gloss, is distinguished by many things; but according to the Apostle's intent, it does not seem that in this place attention is paid to more than one reason. …

Commentary on 1 Corinthians ↗