Jami` at-Tirmidhi 236
جامع الترمذي#236SahihAbu Hurairah narrated that :the Prophet said: "When one of you leads the people in prayer then let him be brief, for indeed here are among them the young and the old, the weak and the ill. When one of you prays alone, then let him pray as he wishes
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 2:88