The Saying of Allah Most High: "... And as for those who can fast with difficulty, they have) a choice either to fast or) to feed a Miskin (poor person) (for every day)" is Abrogated by His saying: "... So whoever of you sights (the crescent on the first night of) the month (of Ramadan i.e. is present at his home), he must observe Sawm (fasts) that month"...

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا بَكْرٌ، - يَعْنِي ابْنَ مُضَرَ - عَنْ عَمْرِو بْنِ الْحَارِثِ، عَنْ بُكَيْرٍ، عَنْ يَزِيدَ، مَوْلَى سَلَمَةَ عَنْ سَلَمَةَ بْنِ الأَكْوَعِ، - رضى الله عنه - قَالَ لَمَّا نَزَلَتْ هَذِهِ الآيَةُ ‏{‏ وَعَلَى الَّذِينَ يُطِيقُونَهُ فِدْيَةٌ طَعَامُ مِسْكِينٍ‏}‏ كَانَ مَنْ أَرَادَ أَنْ يُفْطِرَ وَيَفْتَدِيَ ‏.‏ حَتَّى نَزَلَتِ الآيَةُ الَّتِي بَعْدَهَا فَنَسَخَتْهَا ‏.‏