The Messenger of Allah (ﷺ) 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 (ﷺ) 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).