Sahih Muslim , Book 6, Hadith 2548 (USC-MSA) ⓘ

Salama b. Akwa' reported: We, during the lifetime of the Messenger of Allah, in one month of Ramadan (observed fast according to our liking). He who wished to fast lasted and he who wished to break broke it and fed a needy person as an expiation 1544 till this verse was revealed:" He who witnesses among you the month (of Ramadan) he should observe fast during it" (ii. 184).

حَدَّثَنِي عَمْرُو بْنُ سَوَّادٍ الْعَامِرِيُّ، أَخْبَرَنَا عَبْدُ اللَّهِ بْنُ وَهْبٍ، أَخْبَرَنَا عَمْرُو بْنُ، الْحَارِثِ عَنْ بُكَيْرِ بْنِ الأَشَجِّ، عَنْ يَزِيدَ، مَوْلَى سَلَمَةَ بْنِ الأَكْوَعِ عَنْ سَلَمَةَ بْنِ الأَكْوَعِ، - رضى الله عنه - أَنَّهُ قَالَ كُنَّا فِي رَمَضَانَ عَلَى عَهْدِ رَسُولِ اللَّهِ صلى الله عليه وسلم مَنْ شَاءَ صَامَ وَمَنْ شَاءَ أَفْطَرَ فَافْتَدَى بِطَعَامِ مِسْكِينٍ حَتَّى أُنْزِلَتْ هَذِهِ الآيَةُ ‏{‏ فَمَنْ شَهِدَ مِنْكُمُ الشَّهْرَ فَلْيَصُمْهُ‏}‏