The World Federation One Stop Fiqh

Ruling 794

If someone has a doubt about his body or clothing being pure, in the event that he investigates and does not see anything on it and performs prayers, and after prayers he realises that his body or clothing was impure, his prayers are valid. However, if he does not investigate, then based on obligatory precaution he must perform his prayer again; and in the event that the time has expired, he must make it up.