Al-Baqarah · 2:184

184. You are ordered to fast for a small number of days in the year. Yet whoever of you is ill, with an illness that makes fasting difficult, or travelling, then they do not need to fast; but they can make up for these days by fasting the same number of other days. Those who are able to fast, but do not, should compensate by feeding a poor person for every day they did not fast. Fasting is better for you than not fasting and feeding a poor person instead, if you only knew what goodness there is in fasting. This was the first of Allah’s laws about fasting: whoever wanted to fast did so; and whoever did not want to fast was permitted not to, and fed a poor person instead. Afterwards Allah made fasting a duty for every able person who has reached puberty.