Musnad Ahmad #82

Shu'bah said: I heard 'Asim bin 'Amr al-Bajali narrate from one of those who asked ‘Umar bin al-Khattab. We have come to you to ask you about three things: A man's nafl prayer in his house, Ghusl in the case of janabah, and what it is appropriate for a man to do with his wife when she is menstruating. He said: Are you magicians? You have asked me about something that no one has asked me about since I asked the Messenger of Allah (ﷺ) about it, and he said: `A man's nafl prayer in his house is light, so whoever wishes, let him illuminate his house.` And he said with regard to ghusl in the case of janabah: `Let him wash his private parts, then do wudoo', then pour water over his head three times.` And he said concerning the menstruating woman: `The whatever is above the izar (waist wrapper).`