Surah Al-Baqarah, ayah 185

شَهۡرُ رَمَضَانَ ٱلَّذِيٓ أُنزِلَ فِيهِ ٱلۡقُرۡءَانُ هُدٗى لِّلنَّاسِ وَبَيِّنَٰتٖ مِّنَ ٱلۡهُدَىٰ وَٱلۡفُرۡقَانِۚ فَمَن شَهِدَ مِنكُمُ ٱلشَّهۡرَ فَلۡيَصُمۡهُۖ وَمَن كَانَ مَرِيضًا أَوۡ عَلَىٰ سَفَرٖ فَعِدَّةٞ مِّنۡ أَيَّامٍ أُخَرَۗ يُرِيدُ ٱللَّهُ بِكُمُ ٱلۡيُسۡرَ وَلَا يُرِيدُ بِكُمُ ٱلۡعُسۡرَ وَلِتُكۡمِلُواْ ٱلۡعِدَّةَ وَلِتُكَبِّرُواْ ٱللَّهَ عَلَىٰ مَا هَدَىٰكُمۡ وَلَعَلَّكُمۡ تَشۡكُرُونَ ١٨٥

Shahru ramadānal-ladhī unzila fīhil-qur'ānu hudal lin-nāsi wabayyinātim minal-hudā wal-furqāni faman shahida minkumush-shahra falyasumhu waman kāna marīdan aw 'alā safarin fa'iddatum min ayyāmin ukhara yurīdullāhu bikumul-yusra walā yurīdu bikumul-'usra walitukmilul-'iddata walitukabbirullāha 'alā mā hadākum wala'allakum tashkurūn

The month of Ramaḍān [is that] in which was revealed the Qur’ān, a guidance for the people and clear proofs of guidance and criterion. So whoever sights [the crescent of] the month,⁶⁶ let him fast it; and whoever is ill or on a journey - then an equal number of other days. Allāh intends for you ease and does not intend for you hardship and [wants] for you to complete the period and to glorify Allāh for that [to] which He has guided you; and perhaps you will be grateful.