וְיִתְכַּסּ֣וּ שַׂקִּ֗ים הָֽאָדָם֙ וְהַבְּהֵמָ֔ה וְיִקְרְא֥וּ אֶל־אֱלֹהִ֖ים בְּחָזְקָ֑ה וְיָשֻׁ֗בוּ אִ֚ישׁ מִדַּרְכּ֣וֹ הָֽרָעָ֔ה וּמִן־הֶחָמָ֖ס אֲשֶׁ֥ר בְּכַפֵּיהֶֽם׃
but let them be covered with sackcloth, both man and beast, and let them cry mightily unto God; yea, let them turn every one from his evil way, and from the violence that is in their hands.
Read halakhic rulings (Jewish law) on Jonah 3:8: and classical halakhic sources.