The Islamic ruling is that clothes do not become impure if a fly or mosquito sits on them during relieving oneself, even if there is a small amount of impurity on its legs. Islamic scholars state that this kind of small impurity is forgiven in Shariah. It is very hard to avoid flies and mosquitoes because they land on impurities and then fly to clothes or water. Due to this difficulty, such minor impurity is excused. This explanation is mentioned in the fatwa and supported by the statement of Imam al Rafai رحمه الله.