‘Abdullah b. Abu’l-Qais (RA) reported: I asked ‘A’isha (RA) about the Witr (prayer) of the Messenger of Allah (ﷺ) and made mention of a hadith, then I said: What did he do after having sexual intercourse? Did he take a bath before going to sleep or did he sleep before taking a bath? She said: He did all these. Sometimes he took a bath and then slept, and sometimes he performed ablution only and went to sleep. I (the narrator) said: Praise be to Allah Who has made things easy (for human beings).
Sahih Muslim 307a, Book 3, Hadith 27