107 – Abu Hurayrah reports that the Messenger of Allah ﷺ said, “Under every strand of hair there is a state of janābah (major ritual impurity); so wash the hair and cleanse the skin.” It was transmitted by Abu Dawud and al-Tirmidhi, who both graded it weak (1).

Ahmad records a similar report from ʿĀʾishah, but its chain contains an unidentified narrator (2).

Status of the hadith
The narration is weak, for it comes through al-Hārith ibn Wajīh. Abu Dawud said, “His ḥadith is munkar; he is weak,” and al-Tirmidhi commented, “It is gharīb; we know it only through al-Hārith, and the shaykh is not reliable.” Al-Shafiʿi declared, “This ḥadith is not established,” while al-Bayhaqi stated, “The scholars of ḥadith—such as al-Bukhari, Abu Dawud, and others—rejected it.”

As for the report from ʿĀʾishah preserved by Imam Ahmad, its isnād includes an unknown transmitter, and the anonymity of a narrator other than a Companion renders the ḥadith weak.

Despite this weakness, Ibn Ḥajar, after discussing it in al-Talkhīs al-Ḥabīr, said: “In this regard there is also a narration from ʿAli, traced back to the Prophet ﷺ: ‘Whoever leaves unwashed even the space of a single hair while in a state of janābah will suffer such-and-such.’ Its chain is sound; Abu Dawud (249) and Ibn Mājah (2599) recorded it, though it has been said that the correct view is that it is actually the statement of ʿAli himself.”

I say: Stopping the chain at ʿAli does not lessen its authority, for the ruling has the force of a marfūʿ report—being a matter that cannot be reached by personal reasoning. And Allah knows best.