Sahih Muslim 1747
صحيح مسلم#1747SahihZaid b. Arqam reported that the Messenger of Allah (ﷺ) went out to the people of Quba' and saw them observing prayer; upon this he said:The prayer of the penitent should be observed when the young weaned camels feel heat of the sun
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: 6:176