Sunan Abi Dawud 2862
سنن أبي داود#2862SahihNarrated 'Abdullah bin 'Umar:The Messenger of Allah (ﷺ) as saying: It is the duty of a Muslim man who has something which is to be given as bequest not to have it for two nights without having his will written regarding it
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 ArnautSahih
Zubair Ali ZaiSahih Bukhari (2738) Sahih Muslim (1627)
In-book reference: 18:1