Sahih Muslim 2745
صحيح مسلم#2745SahihImran b. Husain (Allah be pleased with them) reported that the Messenger of Allah (ﷺ) said to him (or he said to another person and he was listening to it):O, so and so, did you observe fast in the middle of the month? He said: No. Thereupon he (the Messenger of Allah) said: When you break it, then observe fast for two days
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 13:251