Sunan at-Tirmithiy كتاب الصوم باب ما جاء ( وعلى الذين يطيقونه )
Salamah [Ibn-'Amr] Ibnul-Akwa' said, "When the Qur'ānic verse: And upon those who are able [to fast, but with hardship] - a ransom [as substitute] of feeding a poor person [each day] (2 [al-Baqarah]: 184) was revealed, those of us who opted not to fast would feed a poor person instead, until the next Qur'ānic verse (of the chapter) was revealed and superseded it (1)." Footnotes: (1) So whoever sights [the new moon of] the month, let him fast it; (2 [al-Baqarah]: 185). After this verse was revealed it was no longer permissible to feed a poor person instead of fasting, when one is capable of fasting. Click on ḥadīth to read more