Q: For security concerns, we want to place a mirror in front of where we pray so we can see who is coming in and out. Is this permissible?

A: It is considered makrooh (disliked) to intentionally place a mirror in front of you while praying. Actively looking at yourself in a mirror during prayer is considered a sin and can potentially invalidate the salah.

If security is a legitimate concern, Islam permits having a group of individuals be as lookouts while others engage in prayer. This way, you can ensure security without compromising the sanctity of your prayer.

Allah Certainly Knows Best.

P.s. I am still trying to figure out, how can a mirror prevent and actively violent individual perusing tragedy.