Al-Baqarah 2:184
أَيَّامًا مَّعْدُودَاتٍ ۚ فَمَن كَانَ مِنكُم مَّرِيضًا أَوْ عَلَىٰ سَفَرٍ فَعِدَّةٌ مِّنْ أَيَّامٍ أُخَرَ ۚ وَعَلَى الَّذِينَ يُطِيقُونَهُ فِدْيَةٌ طَعَامُ مِسْكِينٍ ۖ فَمَن تَطَوَّعَ خَيْرًا فَهُوَ خَيْرٌ لَّهُ ۚ وَأَن تَصُومُوا خَيْرٌ لَّكُمْ ۖ إِن كُنتُمْ تَعْلَمُونَ ١٨٤
Ayyaman maAAdoodatin faman kana minkum mareedan aw AAala safarin faAAiddatun min ayyamin okhara waAAala allatheena yuteeqoonahu fidyatun taAAamu miskeenin faman tatawwaAAa khayran fahuwa khayrun lahu waan tasoomoo khayrun lakum in kuntum taAAlamoona
(These are) a fixed number of days. So, whoever amongst you is ill or on a journey, then he shall complete fasting for the fixed number by (fasting on) other days. But those who are not able to fast, it is obligatory on them to provide food for a needy person in lieu of that. But whoever does (greater) good seeking pleasure, that is better for him. And your fasting is better for you if you understand. (2:184)