Compiled by Imam Abu Dawud as-Sijistani
حَدَّثَنَا مُحَمَّدُ بْنُ الْمِنْهَالِ، حَدَّثَنَا يَزِيدُ بْنُ زُرَيْعٍ، حَدَّثَنَا سَعِيدٌ، عَنْ قَتَادَةَ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ مَسْلَمَةَ، عَنْ عَمِّهِ، أَنَّ أَسْلَمَ، أَتَتِ النَّبِيَّ صلى الله عليه وسلم فَقَالَ " صُمْتُمْ يَوْمَكُمْ هَذَا " . قَالُوا لاَ . قَالَ " فَأَتِمُّوا بَقِيَّةَ يَوْمِكُمْ وَاقْضُوهُ " . قَالَ أَبُو دَاوُدَ يَعْنِي يَوْمَ عَاشُورَاءَ .
AbdurRahman reported on the authority of his uncle that the people of the tribe Aslam came to the Prophet (ﷺ). He said (to them): Did you fast on this day? They replied: No. He said: Complete the rest of your day, and make atonement for it.