Sayyiduna Abdullah bin Busr al-Sulami (may Allah be pleased with him) narrates from his sister al-Samma' that the Prophet (peace and blessings be upon him) said: "Do not fast on Saturday except for what has been made obligatory upon you; and if one of you finds nothing (to break the fast with) except the bark of a grapevine or a twig of a tree, let him chew it." This hadith is sahih (authentic) on the condition of Imam Bukhari, but they did not record it. However, there is an authentic hadith contrary to it which the two Shaykhs have recorded, namely the narration of Sayyidah Juwayriyah bint al-Harith (may Allah be pleased with her) that the Prophet (peace and blessings be upon him) came to her on a Friday while she was fasting, and he (peace and blessings be upon him) asked: "Did you fast yesterday?" She said: No. He (peace and blessings be upon him) said: "Do you intend to fast tomorrow (Saturday)?" (Then he mentioned the full hadith, in which there is no prohibition of fasting on Saturday; rather, it mentions the prohibition of singling out Friday for fasting.)

It is narrated from Imam Ibn Shihab al-Zuhri (may Allah have mercy on him) that when the prohibition of fasting on Saturday was mentioned before him, he said: "This is a narration of the people of Hims (that is, its authenticity has been questioned)." And in contrast to it there is another narration with an authentic chain: