Sunan Abi Dawud 255
سنن أبي داود#255SahihNarrated Thawban: Shurayh ibn Ubayd said: Jubayr ibn Nufayr gave me a verdict about the bath because of sexual defilement that Thawban reported to them that they asked the Prophet (ﷺ) about it. He (the Prophet) replied: As regards man, he should undo the hair of his head and wash it until the water should reach the roots of the hair. But there is no harm if the woman does not undo it (her hair) and pour three handfuls of water over her head
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautHasan
Zubair Ali ZaiIsnaad Hasan
In-book reference: 1:255