John 12:37

(Hom. lxviii. 1) And thus the Evangelist tacitly explains it, when he adds, But though He had done so many miracles before them, yet they believed not on Him.

(Tr. liii. 2) But some mutter, and ask, What fault was it of the Jews, if it was necessary that the sayings of Esaias should be fulfilled? We answer, that God, foreseeing the future, predicted by the Prophet the unbelief of the Jews, but did not cause it. God does not compel men to sin, because He knows they will sin. He foreknows their sins, not His own. The Jews committed the sin, which He who knows all things foretold they would commit.

There are some, then, who mutter among themselves, and sometimes speak out when they can, and even break forth into turbulent debate, saying: What did the Jews do, or what fault was it of theirs, if it was a necessity "that the saying of Isaiah the prophet should be fulfilled, which he spake, Lord, who hath believed our report and to whom hath the arm of the Lord been revealed?" To whom our answer is, that the Lord, in His foreknowledge of the future, foretold by the prophet the unbelief of the Jews; He foretold it, but did not cause it. For God does not compel any one to sin simply because He knows already the future sins of men. For He foreknew sins that were theirs, not His own; sins that were referable to no one else, but to their own selves. Accordingly, if what He foreknew as theirs is not really theirs, then had He no true foreknowledge: but as His foreknowledge is infallible, it is doubtless no one else, but they themselves, whose sinfulness God foreknew, that are the sinners. The Jews, therefore, committed sin, with no compulsion to do so on His part, to whom sin is an object of displeasure; but He foretold their committing of it, because nothing is concealed from His knowledge. And accordingly, had they wished to do good instead of evil, they would not have been hindered; but in this which they were to do they were foreseen of Him who knows what every man will do, and what He is yet to render unto such an one according to his work.

He means the miracles related above. It was no small wickedness to disbelieve against such miracles as those.