Narrated 'Aishah: The Prophet (ﷺ) as saying: If anyone dies when some fast due from him has been unfulfilled, his heir must fast on his behalf
SahihSahihSahih Bukhari (1952) Sahih Muslim (1147)Book 22 · Hadith 70
سنن أبي داود
Narrated 'Aishah: The Prophet (ﷺ) as saying: If anyone dies when some fast due from him has been unfulfilled, his heir must fast on his behalf