6 – From a man who had accompanied the Prophet ﷺ: “The Messenger of Allah ﷺ forbade a woman to bathe with water left over by a man, or a man with water left over by a woman. Instead, let them both draw fresh water together.” Recorded by Abu Dawud and al-Nasa’i, and its isnad is authentic. (1)

Status of the hadith
The report is sahih (sound). Al-Shawkani, in summary, notes that al-Bayhaqi regarded it as effectively mursal, while Ibn Hazm alleged that the transmitter Dawud who narrates from Humayd ibn ‘Abd al-Rahman al-Himyari is weak. Ibn Hajar states in Fath al-Bari (1/300): “Its narrators are reliable, and I have found no convincing evidence from those who have criticised it.”
Al-Bayhaqi’s claim that it is mursal is rejected, because an unnamed Companion does not weaken a chain. Ibn Hazm’s assertion that the narrator Dawud is Dawud ibn Yazid al-Awdi—who is indeed weak—is likewise dismissed; the narrator is actually Dawud ibn ‘Abd Allah al-Awdi, who is trustworthy, as Abu Dawud and others clearly identified him by his father’s name.
Al-Hafiz Ibn Hajar also states in Bulugh al-Maram that its isnad is authentic. Ibn ‘Abd al-Hadi remarks in al-Muharrar that al-Humaydi declared it sound, and al-Bayhaqi added, “Its narrators are reliable.”

Vocabulary of the hadith
nahā (he forbade): a statement that demands abstention in a commanding manner, expressed in the present-tense verb preceded by the prohibitive particle lā.