As-Samma’ bint Busr (RAA) narrated that The Messenger of Allah (ﷺ) said:

"Do not fast on Saturday unless it is an obligatory fast. (Do not fast) even if you do not find anything (to eat) except for some grape peelings or the branch of a tree, in that case he should chew on it." Related by the five Imams and its narrators are reliable. Imam Malik disapproved this narration, and Abu Dawud said that this narration is abrogated.

وَعَنِ اَلصَّمَّاءِ بِنْتِ بُسْرٍ رَضِيَ اَللَّهُ عَنْهَا أَنَّ رَسُولَ اَللَّهِ ‏- صلى الله عليه وسلم ‏-قَالَ: { لَا تَصُومُوا يَوْمَ اَلسَّبْتِ, إِلَّا فِيمَا اِفْتُرِضَ عَلَيْكُمْ, فَإِنْ لَمْ يَجِدْ أَحَدُكُمْ إِلَّا لِحَاءَ عِنَبٍ, أَوْ عُودَ شَجَرَةٍ فَلْيَمْضُغْهَا } رَوَاهُ اَلْخَمْسَةُ, وَرِجَالُهُ ثِقَاتٌ, إِلَّا أَنَّهُ مُضْطَرِبٌ [1]‏ .‏ وَقَدْ أَنْكَرَهُ مَالِكٌ [2]‏ .‏ وَقَالَ أَبُو دَاوُدَ: هُوَ مَنْسُوخٌ [3]‏ .‏