שולחן ערוך אורח חיים · סימן תקע״ח

English

"That every individual should fast and pray for their distress. In one section: Just as the community fasts and prays for their troubles, so too, each individual should fast and pray for their own distress. For example, if one is sick, lost in the wilderness, or imprisoned in a prohibited place, they should engage in fasting and seek mercy during their fast. However, one should not fast on Shabbat, Festivals, Chanukah, Purim, and Rosh Chodesh.