Musnad Ahmad 453:1

Humaid ibn Abd al-Rahman al-Ru’asi narrated to us, Zuhayr narrated to us, from Dawud ibn Abd Allah al-Awdi, from Humaid al-Himyari, who said: I met a man from the companions of the Prophet, may Allah bless him and grant him peace, who accompanied him just as Abu Hurayrah accompanied him. He did not add more than three words for me. He said: The Messenger of Allah, may Allah bless him and grant him peace, said: "A man should not perform ghusl with the leftover water of his wife, nor should she perform ghusl with his leftover water, and he should not urinate in his place of bathing, and he should not comb his hair every day."