Sayyiduna Abu Hurairah (may Allah be pleased with him) said: "When a person is not healthy between two Ramadans, then he will fast the current Ramadan (i.e., the missed fasts), and for the previous Ramadan he will feed (the poor), and making up (the missed fasts) of the previous Ramadan will not be obligatory upon him. But if a person is healthy and does not fast, until the next Ramadan comes, then he will fast the current Ramadan, then as compensation for the previous Ramadan's fasts, he will feed the poor, and when he completes the fasts of this month, then he will make up the missed fasts of the previous Ramadan." Its chain is authentic.