If one washes himself after using the toilet (istinjaa’) but then notices traces of feces on one’s underwear after praying. Should one re-do the prayer?
The Scholars say that if a person discovered after prayer that there was impurity on his body or clothes, this does not affect the prayer. No repeat is requested. However, if a person remembered that he was not in a state of purity, ie. having wudu, then in this case he has to repeat the prayer.