To make up for the missed days of fasting

وَقَالَ ابْنُ عَبَّاسٍ لاَ بَأْسَ أَنْ يُفَرَّقَ لِقَوْلِ اللَّهِ تَعَالَى: {فَعِدَّةٌ مِنْ أَيَّامٍ أُخَرَ} وَقَالَ سَعِيدُ بْنُ الْمُسَيَّبِ فِي صَوْمِ الْعَشْرِ لاَ يَصْلُحُ حَتَّى يَبْدَأَ بِرَمَضَانَ.Ibn ‘Abbas رضي الله عنهما said, “There is no harm to observe fasting intermittently, as the Statement of Allah تعالى shows: ‘... The same number [of days which one did not observe Saum (fasts) must be made up] from other days...’” Sa‘id bin Al-Musaiyab said: “The ten days of Saum (fasting) (as Nawafil of Dhul-Hijjah) should not be observed till the fasting in lieu of the missed days of Ramadan were completed.” Ibrahim said: “If somebody did not observe Saum (fast) in lieu of the missed days of Ramadan till the next Ramadan came, then he should observe Saum (fast) the present Ramadan and then the missed days of the previous Ramadan.” Ibrahim did not think that that person should feed the poor (as Fidya). Narrated Abu Hurairah indirectly on the authority of the Prophet ﷺ and Ibn ‘Abbas that he should feed the poor. But Allah does not mention the feeding of the poor but only says: ‘... The same number [of days which one did not observe Saum (fasts) must be made up] from other days...’