It is narrated from Sayyiduna Abu Laila (may Allah be pleased with him), he says: We were with the Noble Prophet (peace and blessings be upon him), when Sayyiduna Hasan bin Ali (may Allah be pleased with him) came crawling and climbed onto the chest of the Prophet (peace and blessings be upon him) and urinated on him. I saw the urine on the stomach of the Prophet (peace and blessings be upon him). So we rushed towards the Messenger of Allah (peace and blessings be upon him) to catch him, but the Noble Prophet (peace and blessings be upon him) said: "My son, my son." In another narration it is: "Leave my son and do not alarm him, until he finishes urinating." Then the Prophet (peace and blessings be upon him) called for water and poured it over it.