"The Prophet would glance during Salat" and he mentioned a similar narration.
Jami` at-Tirmidhi Book 6, Hadith 45
← Previous Hadith "The Messenger of Allah would glance toward the right and the left during Salat but he would not turn his neck to look behind him."

Jami` at-Tirmidhi Book 6, Hadith 44 Next Hadith → "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)

Jami` at-Tirmidhi Book 6, Hadith 46