The divine word says in a certain place: In the days of your solemnities afflict your souls (Lev. 16:29; 23:27). Why did it say this? Because fasts and vigils and holy afflictions waste away the lowly [or: humbled] body, but purify defiled hearts, and so forth. See these homilies in volume L of the Patrology, among the Works of St. Eucherius, to whom they are also ascribed, columns 844, 848, 855, 857.