Yosef Karo, Translation:Shulchan Aruch — Orach Chaim 579…
“ Rather, it is repentance and good deeds, for it does not say regarding the people of Ninveh, 'God saw their sackcloth and fasts' but instead 'God saw their deads' [Jonah 3:10] . In the tradition, it says 'Tear your hearts and not your garments' [Joel 2:13] ." He continues with things of this vein according to his ability until their hearts are subdued and they will repent fully. After he finishes his words of submission, they stand for prayer. They have a prayer leader stand up who is fitting to pray on a fast day. If the one who said the words of submissions is qualified to pray, he prays. ”
