Sunan Abi Dawud 53
سنن أبي داود#53SahihNarrated Aisha, Ummul Mu'minin: The Messenger of Allah (ﷺ) said: Ten are the acts according to fitrah (nature): clipping the moustache, letting the beard grow, using the tooth-stick, cleansing the nose (Al-Istinshaq) with water, cutting the nails, washing the finger joints, plucking the hair under the arm-pits, shaving the pubes, and cleansing one's private parts (after easing or urinating) with water. The narrator said: I have forgotten the tenth, but it may have been rinsing the mouth
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniHasan
Muhammad Muhyi Al-Din Abdul HamidSahih
In-book reference: 1:53