Sahih Bukhari Volume 6, Book 60, Hadith Number 34.

Narrated By 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.