Q. If a person looked at his watch on his hand and understood the time in Salaah, is a person’s Salaah valid?
A. During Salaah, one should insure that he/she maintains complete devotion without being distracted by anything outside of Salaah.
It will be Makrooh (disliked) to look at the clock/watch intentionally during Salaah. If it was done unintentionally, it will not be Makrooh (disliked). In either, case, the Salaah will remain valid. (Shaami 1/634)
Allah Ta’ala Knows Best
Mufti Ismaeel Bassa