Ruling 172 — Purification (Ṭahārah)

If a person washes an object with water and he becomes certain that it has become pure, but afterwards he doubts whether he removed the intrinsic impurity from it or not, he must rewash it with water until he is certain or confident that the intrinsic impurity has been removed. However, if he suffers from obsessive doubting (waswās), he must not heed his doubt.