Sahih Muslim 1583
صحيح مسلم#1583SahihYahya b. Yazid al-Huna'i reported:I asked Anas b. Malik about shortening of prayer. He said: When the Messenger of' Allah (ﷺ) had covered a distance of three miles or three farsakh (Shu'ba, one of the narrators, had some doubt about it) he observed two rak'ahs
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: 6:14