Sahih Bukhari
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
Volume: 005 / Book Number: 059 / Hadith Number: 737
Narrated Talha:
I asked 'Abdullah bin Abu 'Aufa "Did the Prophet make a will? ' He replied, "No." I further asked, "How comes it that the making of a will was enjoined on the people or that they were ordered to make it? " He said, "The Prophet made a will concerning Allah's Book."