Sayyiduna Ibn Abbas (may Allah be pleased with them both), explaining the words of Allah Almighty: "And upon those who are able to fast" [Surah al-Baqarah: 184], said: that is, those upon whom fasting is imposed with hardship. "A ransom: the feeding of a poor person" [Surah al-Baqarah: 184], that is, the food of one poor person. "But whoever volunteers good" [Surah al-Baqarah: 184], that is, he adds the food of another poor person; this ruling has not been abrogated. "It is better for him" [Surah al-Baqarah: 184]: this concession is only for the elderly person who is unable to fast, or a sick person who is certain that he will not recover.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11340