If he does ask, Ibn Aqil said: The person being asked is not required to provide an answer, due to the report of Umar. It is possible that he is required to do so, because he was asked about a condition of prayer, so it becomes mandatory for him to answer if he knows, just as if he were asked about the direction of prayer (qibla). The report of Umar indicates that the leavings (su'r) of predatory animals are not impure. And Allah knows best.