Hafs bin 'Umar bin al-Harith حفص بن عمر بن الحارث · Fasting (Kitab Al-Siyam)

The Messenger of Allah (ﷺ) had himself cupped when he was fasting. Abu Dawud said: Wuhaib b. Khalid narrated a similar tradition from Ayyub through a different chain of narrators. Ja'far b. Rabi'ah and Hisham, that is, Ibn Hassan, narrated a similar tradition from 'Ikrimah on the authority of Ibn 'Abbas.

The Prophet (ﷺ) said: Do not fast on Saturday except what has been made obligatory on you; and if one of you can get nothing but a grape skin or a piece of wood from a tree, he should chew it.