The Book of Fasting
22/63. Chapter:
Interpreting the saying of Allah, The Mighty And Sublime: "And as for those who can fast with difficulty,(e.g. an old man), they have (a choice either to fast or) to feed a Miskin (poor person) (for every day)"
Sunan an-Nasai
أَخْبَرَنَا قُتَيْبَةُ، قَالَ أَنْبَأَنَا بَكْرٌ، - وَهُوَ ابْنُ مُضَرَ - عَنْ عَمْرِو بْنِ الْحَارِثِ، عَنْ بُكَيْرٍ، عَنْ يَزِيدَ، مَوْلَى سَلَمَةَ بْنِ الأَكْوَعِ عَنْ سَلَمَةَ بْنِ الأَكْوَعِ، قَالَ لَمَّا نَزَلَتْ هَذِهِ الآيَةُ { وَعَلَى الَّذِينَ يُطِيقُونَهُ فِدْيَةٌ طَعَامُ مِسْكِينٍ } كَانَ مَنْ أَرَادَ مِنَّا أَنْ يُفْطِرَ وَيَفْتَدِيَ حَتَّى نَزَلَتِ الآيَةُ الَّتِي بَعْدَهَا فَنَسَخَتْهَا .
It was narrated that salamah bin Al-Akwa said: "When this verse was revealed 'And as for those who can fast with difficulty, (e.g. an old man), they have (a choice either to fast or) to feed a miskin (poor person) (for every day). Those among us who did not want to fast would pay the fidyah, until the verse after it was revealed and abrogated this."
Reference : Sunan an-Nasa'i 2316In-book reference : Book 22, Hadith 227English translation : Vol. 3, Book 22, Hadith 2318