Sahih Muslim 1769
صحيح مسلم#1769SahihJabir reported:The Messenger of Allah (ﷺ) was asked about the prayer which was most excellent. He said: That in which the standing is longer. (This hadith is narrated by another chain of transmitters too)
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: 6:198