Sunan Ibn Majah, Chapter: The Chapters on Hajj

"Abu Musa Al-Ashari used to issue rulings concerning Tamattu'. Then a man said to him: 'Withhold some of your rulings, for you do not know what the Commander of the Believers has introduced into the rites after you.' (Abu Musa said:) 'Then when I met him later on, I asked him.' Umar said: 'I know that the Messenger of Allah (saw) and his Companions did it, but I did not like that people should lie with their wives in the shade of the Arak trees and then go out for Hajj with their heads dripping,' (i.e. due to the bath after sexual relations)."