Sahih Bukhari Volume 6, Book 61, Hadith Number 540.

Narrated By Talha : I asked ‘Abdullah bin Abi ‘Aufa, “Did the Prophet make a will (to appoint his successor or bequeath wealth)?” He replied, “No.” I said, “How is it prescribed then for the people to make wills, and they are ordered to do so while the Prophet did not make any will?” He said, “He made a will wherein he recommended Allah’s Book.”