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.
Sahih al-Bukhari Book 65, Hadith 34
← Previous Hadith Ibn `Umar recited: "They had a choice, either fast or feed a poor for every day.." and added, "This Verse is abrogated."

Sahih al-Bukhari Book 65, Hadith 33 Next Hadith → When the order of compulsory fasting of Ramadan was revealed, the people did not have sexual relations with their wives for the whole month of Ramadan, but some men cheated themselves (by violating that restriction). So Allah revealed: "Allah is aware that you were deceiving yourselves but He accepted your repentance and forgave you.." (3.187)

Sahih al-Bukhari Book 65, Hadith 35