ציטירנדיקער פּירוש אויף יונה 3:5

Tractate Taanit is about the practice of fasting and offering special prayers in times of trouble, especially during a drought. The Bible is full of examples of the Israelites fasting, praying and engaging in other forms of supplication in order to entreat God to respond to their needs. The most famous of these cases is probably Esther who calls for a three-day fast to ensure her success and safety when entering in to speak to the king. See also Joel 1:14; Jeremiah 14:11-12; Jonah 3:5-8; Nehemiah 9:1; Daniel 9:3 and others.

Abarbanel notes that Yonah 3:5 states that the people of Nineveh believed in Hashem and does not state that they believed in Yonah. This conveys the message that they grasped that Yonah was an authentic transmitter of the message of Hashem. It was the authenticity of the Godly message that convinced the people of Nineveh, not the result of a seductive and intoxicating manipulation by a gifted speaker.

They trusted in haShem - "the men of Nineveh trusted in haShem" [Yonah 3:5]. As is stated in the midrash [Pirkei deRabbi Eliezer 43]: "not one of them remained" [Exodus 14:28] - none remained except one, and that was Par'oh, and he walked to Nineveh and ruled there. And this is "the men of Nineveh trusted in haShem": he was reminded of what he had seen in Mitzrayim and at the sea.