Sunan Ibn Majah 1726
سنن ابن ماجه#1726SahihIt was narrated from ‘Abdullah bin Busr that the Messenger of Allah (ﷺ) said:“Do not fast on Saturdays apart from days when you are obliged to fast. If anyone of you cannot find anything other than grape stalks or the bark of a tree, let him suck on it.” Another chain from 'Abdullah bin Busr, from his sister who said: "The Messenger of Allah (ﷺ) said," and he mentioned similarly
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Fouad Abd al-BaqiSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiIsnaad Hasan
In-book reference: 7:89