Al-Husayn ibn Said, from Ahmad ibn Muhammad, who said: I (narrator) asked Abu al-Hasan عليه السلام, peace be upon him, about ‘fasting in Makkah and al-Madinah while we are travelling.’ Imam عليه السلام said: “An obligation?” So I (narrator) asked: “No, but rather it is voluntary, just as prayer is performed voluntarily.” Imam عليه السلام said: “You say, ‘Today and tomorrow’?” I (narrator) asked: “Yes.” Imam عليه السلام said: “Do not fast.”