Surah Al-Baqarah (The Cow), Verse 184

اَیَّامًا مَّعْدُوْدٰتٍ فَمَنْ كَانَ مِنْكُمْ مَّرِیْضًا اَوْ عَلٰی سَفَرٍ فَعِدَّةٌ مِّنْ اَیَّامٍ اُخَرَ وَعَلَی الَّذِیْنَ یُطِیْقُوْنَهٗ فِدْیَةٌ طَعَامُ مِسْكِیْنٍ فَمَنْ تَطَوَّعَ خَیْرًا فَهُوَ خَیْرٌ لَّهٗ وَاَنْ تَصُوْمُوْا خَیْرٌ لَّكُمْ اِنْ كُنْتُمْ تَعْلَمُوْنَ ۟

Ayyaamam ma'doodaat; faman kaana minkum mareedan aw'alaa safarin fa'iddatum min ayyaamin ukhar; wa 'alal lazeena yuteeqoonahoo fidyatun ta'aamu miskeenin faman tatawwa'a khairan fahuwa khairul lahoo wa an tasoomoo khairul lakum in kuntum ta'lamoon

“(Fasting) for a fixed number of days; but if any of you is ill, or on a journey, the prescribed number (Should be made up) from days later. For those who can do it (With hardship), is a ransom, the feeding of one that is indigent. But he that will give more, of his own free will,- it is better for him. And it is better for you that ye fast, if ye only knew.”

Quran 2:184 (Yusuf Ali Translation)