Gregory the Dialogist

And now am I their song, yea, I am become their byword. By which same words that time of Holy Church is set forth, when she is openly derided by the lost; when the wicked gaining ground, faith shall be for a reproach, and truth shall be for a ground of accusation. For so much the more contemptible shall each individual be in proportion as he may be more righteous; and the worse object of abhorrence, the more worthy object of praise. …

Morals on the Book of Job, Book XX ↗

Thomas Aquinas

As a consequence he shows what Job had suffered from them, and first he shows that he was derided by them by mouth both in their jokes, so he says, "Now I have been turned into a verse in their songs," because they made up mocking lampoons about him. They also derided him in serious things, and he continues expressing this, "and I have become a proverb for them," because they commonly used the misfortunes of Job like proverbs, giving him as an example of fault and unhappiness.

Commentary on Job ↗