 the reason for this is that their going out is considered disgusting due to their dislike so if it were natural that it would not be possible for them to go out at a time or in a situation that would open the door for them and the same is not true for sweat dirt and the like.
وسبب ذلك أن خروجهما مستقذر لأجل كراهيتهما، فلو كان بالطبع لم يؤمن خروجهما في وقت أو حال يفتح ذلك فيهما، ولا كذلك العرق والوسخ ونحوهما.