Sahih Bukhari
Sahih Bukhari Volume 004, Book 051, Hadith Number 001.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 51. Wills and Testaments (Wasaayaa)
Narated By Abdullah bin Umar : Allah's Apostle said, "It is not permissible for any Muslim who has something to will to stay for two nights without having his last will and testament written and kept ready with him."