It is narrated from Hazrat Abu Saeed Khudri (may Allah be pleased with him) that once we went towards Quba with the Prophet (peace and blessings of Allah be upon him) on a Monday. We passed by Banu Salim, and the Prophet (peace and blessings of Allah be upon him) stopped at the door of Hazrat Ibn Atan (may Allah be pleased with him) and called him by name. At that time, Ibn Atan was fulfilling his desire with his wife. Hearing the voice of the Prophet (peace and blessings of Allah be upon him), he came out dragging his lower garment. The Prophet (peace and blessings of Allah be upon him) saw him in that state and said, "Perhaps we forced you to finish quickly." Ibn Atan (may Allah be pleased with him) asked, "O Messenger of Allah (peace and blessings of Allah be upon him)! Tell me, if a man comes to his wife and there is no ejaculation, what is the ruling?" The Prophet (peace and blessings of Allah be upon him) said, "Ghusl becomes obligatory upon the emission of semen."