Sahih Muslim 4207
صحيح مسلم#4207SahihSalim reported on the authority of his father ('Abdullah b. Umar) that he (his father) had heard Allah's Messenger (ﷺ) as saying:It is not proper for a Muslim who has got something to bequeathe to spend even three nights without having his will written down with him regarding it. 'Abdullah b. 'Umar (Allah be pleased with them) said: Ever since I heard Allah's Messenger (ﷺ) say this I have not spent a night without having my will (written) along with me
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 25:4