Does forgetfulness in prayer invalidate it?

Question:
He says: Honorable Shaykh, may Allah grant you success, if I am forgetful in prayer and think about worldly matters for most of my prayer, does this invalidate the prayer?

Answer:
No, it does not invalidate the prayer, but it invalidates its reward. It invalidates its reward. So the one who thinks during prayer, or has distracting thoughts, or is in this state, does not repeat the prayer, but he has no reward except for the degree to which his heart was present in it. Yes.