Jami` at-Tirmidhi 589
جامع الترمذي#589Da'ifAnas narrated:"The Messenger of Allah said to me: 'O my son! Beware of looking around during the Salat, for indeed looking around during Salat is destruction. If you must do so, then in the voluntary (prayers), not in the obligatory (prayers).'" (Da'if)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirDaif
Al-AlbaniDaif
Zubair Ali ZaiDaif
In-book reference: 6:46