It is narrated from Sayyiduna Muhajir bin Qunfudh (may Allah be pleased with him), he says: I greeted the Noble Prophet (peace and blessings be upon him) with salam while he was performing ablution. The Prophet (peace and blessings be upon him) did not reply to my salam. When he finished his ablution, he said: "What prevented me from replying to your salam was that I was not in a state of purity." In another narration, it is stated: "I disliked mentioning Allah Almighty without being in a state of purity."