Narrated Salama:
When the Divine Revelation: "For those who can fast, they had a choice either fast, or feed a poor for every day," (2.184) was revealed, it was permissible for one to give a ransom and give up fasting, till the Verse succeeding it was revealed and abrogated it.
USC-MSA web (English) reference: Vol. 6, Book 60, Hadith 34
Arabic reference: Book 65, Hadith 4507