Sahih Muslim 2525
صحيح مسلم#2525SahihSa'd b. Abi Waqqas (Allah be pleased with him) said that the Messenger of Allah (ﷺ) struck his hand against the other and (then with the gesture of his two hands) said:The month is thus, thus (two times). He then withdrew (one of) his fingers at the third turn
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: 13:31