Gregory of Nazianzus

Let us sow in tears, so that we may reap in joy. Let us show ourselves people of Nineveh, not of Sodom. Let us amend our wickedness, lest we be consumed with it. Let us listen to the preaching of Jonah, lest we be overwhelmed by fire and brimstone. And if we have departed from Sodom, let us escape to the mountain. Let us flee to Zoar. Let us enter it as the sun rises. Let us not stay in all the plain. …

On His Father's Silence, ORATION 16:14

Cosmas Indicopleustes

But the Chaldaeans and the Medes and Persians, having a somewhat wider knowledge, were instructed by the building of the Tower, and the deluge, and by what happened in the case of Hezekiah and Jonah, and by the Captivity, and by Daniel and the Three Children, and also partly by the writings themselves. In like manner also the Egyptians were instructed by the affairs of Joseph and of Moses, and by the people of Israel, and these nations were thus better prepared for a ready acceptance of Christianity.

The Christian Topography, Book 12 ↗

Ambrose of Milan

If what the Apostle has said is not enough, let them hear the Prophet saying, I chastened myself with fasting. He therefore who fasts not is uncovered and naked and exposed to wounds. And if Adam had clothed himself with fasting he would not have been found to be naked. Nineveh delivered itself from death by fasting. And the Lord Himself says, This kind goeth not out but by prayer and fasting.

Letters, Letter 44 ↗

Jerome

"So the people of Nineveh believed God, and proclaimed a fast, and put on sackcloth, from the greatest of them even to the least of them." LXX: similar. Nineveh believed but Israel did not believe; the foreskin believed, but circumcision remained without faith. First of all the men of Nineveh believed who had arrived at the age of Christ [Eph. 4:13]: they announced a fast and dressed in sackcloth, from the greatest to the smallest of them. …

Commentary on Jonah, Chapter 3 ↗