Musnad Ahmad 2:5

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, he said: I heard ‘Asim ibn ‘Amr al-Bajali narrating from a man from the people who asked ‘Umar ibn al-Khattab. They said to him: "We have only come to you to ask you about three things: about a man’s voluntary prayer in his house, about the ritual bath (ghusl) from sexual impurity (janabah), and about what is permissible for a man from his wife when she is menstruating." He said: "Are you sorcerers? You have asked me about something that no one has asked me about since I asked the Messenger of Allah, peace and blessings of Allah be upon him, about it." He said: "A man’s voluntary prayer in his house is light, so whoever wishes, let him illuminate his house." And he said regarding the ritual bath from sexual impurity: "He washes his private part, then he performs ablution (wudu), then he pours [water] over his head three times." And he said regarding the menstruating woman: "He has what is above the waist-wrapper."