Sunan an-Nasa'i 426
سنن النسائي#426SahihIt was narrated that Jabir said:"When the Messenger of Allah (ﷺ) performed Ghusl, he would pour water on his head three times
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 4:31