Sahih Bukhari
Prophetic Commentary on the Quran (Tafseer of the Prophet (PBUH))
Volume: 006 / Book Number: 060 / Hadith Number: 32
Narrated 'Ata:
That he heard Ibn 'Abbas reciting the Divine Verse:--
"And for those who can fast they had a choice either fast, or feed a poor for every day.." (2.184) Ibn 'Abbas said, "This Verse is not abrogated, but it is meant for old men and old women who have no strength to fast, so they should feed one poor person for each day of fasting (instead of fasting)."