Surah Al Baqarah (184)

Fasting (that is enjoined) is for a certain number of days, but if anyone of you is sick or is on a journey, (he can break his fast), but will still have to fast the same number of days later on; and for those who find it extremely difficult to fast (because of old age or grievous illness) there is an expiation (fidyah)(67), that is, the feeding of a poor man. He who does good (pay the expiation) of his own account more than the stipulated amount, that is better for him; but (nevertheless) to fast is better for you (than submitting an expiation), if you but knew it.