Sahih Bukhari
Sahih Bukhari Volume 003, Book 031, Hadith Number 173.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 31. Fasting
Narated By 'Aisha : Allah's Apostle said, "Whoever died and he ought to have fasted (the missed days of Ramadan) then his guardians must fast on his behalf."