Sahih Muslim | Book 13 | Chapter 1

Narrated by Ibn Umar (Allah be pleased with them)
Ibn Umar (Allah be pleased with them) reported Allah's Messenger (may peace be upon him) as saying: It is the duty of a Muslim who has something which is to be given as a bequest not to have it for two nights without having his will written down regarding it.

Narrated by 'Ubaidullah
This hadith has been narrated on the authority of 'Ubaidullah with the same chain of transmitters, but with a slight variation of words.

Narrated by Nifi
A hadith like this have been narrated on the authority of Nifi, who based his narrations of the words of Ibn 'Umar but with a slight variation of words.
Narrated by Zuhri
Salim reported on the authority of his father ('Abdullah b. Umar) that he (his father) had heard Allah's Messenger (may peace be upon him) as saying: It is not proper for a Muslim who has got something to bequeath 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 (may peace be upon him) say this I have not spent a night without having my will (written) along with me. This hadith has been narrated on the authority of Zuhri with the same chain of transmitters.