Hadith 2677
It is narrated from Sayyiduna Muhajir bin Qunfudh (may Allah be pleased with him) that he greeted the Noble Prophet (peace and blessings be upon him). At that time, the Prophet (peace and blessings be upon him) was urinating, so he did not reply to his greeting. Then the Prophet (peace and blessings be upon him) performed ablution, and then replied to the greeting.