People made a mention of washing because of sexual defilement before the Messenger of Allah (May peace be upon him). The Messenger of Allah (May peace be upon him) said: I pour (water) on my head three times. And he made a sign with both his hands.
Sunan Abi Dawud Book 1, Hadith 239
← Previous Hadith The Messenger of Allah (May peace be upon him) used to take bath with from a vessel (which contained seven to eight seers, i.e., fifteen to sixteen pounds) because of sexual intercourse.

Abu Dawud said: The version narrated by Mu’ammar on the authority of al-Zuhri has: She (‘A’ishah) said: I and the Messenger of Allah (May peace be upon him) took a bath from a vessel which was equal to al-faraq in measurement (i.e., containing water about seven or eight seers).

Abu Dawud said: Ibn ‘Uyainah also narrated like the version of Malik.

Abu Dawud said; I heard Ahmad b. Hanbal say: Al-Faraq contains sixteen rotls (of water). I also heard him say: The sa’of of Ibn Abi Dhi’b contained 5 rotls (of water). The view that a sa’ contains eight rotls (of water) is not safe.

Abu Dawud said: I heard Ahmad (b. Hanbal) say: Whoever gave 5 1/3 rotls (measuring) with our rotl alms of fitr (sadaqat al-fitr), he gave in full, Thereupon he was questioned: Are the dates called al-saihani heavier (can one sa’ of them be given as alms of fitr)? He replied: The dates called al-saihani are good. But I do not know (whether water is heavier or the dates).

Sunan Abi Dawud Book 1, Hadith 238 Next Hadith → when the Messenger of Allah (May peace be upon him) wanted to wash himself because of sexual defilement, he called for a vessel like HILAB (a vessel used for milking the camel). He then took a handful of water and began to pour it on the right side of his head and then on the left side. He then took water in both his hands together and poured it on his head.

Sunan Abi Dawud Book 1, Hadith 240