It 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

English translation · Sunan Ibn Majah