It is narrated from Hazrat Muhajir bin Qunfudh (may Allah be pleased with him) that once I greeted the Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) was performing ablution at that time, so he did not reply. When he had completed the ablution, he replied to my greeting and said: "Nothing prevented me from replying to you except that I did not consider it appropriate to mention the name of Allah while not in a state of purity."