عَنْ بَعْجَةَ بْنِ عَبْدِ اللَّهِ أَنَّ أَبَاهُ أَخْبَرَهُ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ لَهُمْ يَوْمًا: ((هَذَا يَوْمُ عَاشُورَاءَ فَصُومُوا))، فَقَالَ رَجُلٌ مِنْ بَنِي عَمْرِو بْنِ عَوْفٍ: يَا رَسُولَ اللَّهِ! إِنِّي تَرَكْتُ قَوْمِي مِنْهُمْ صَائِمٌ، وَمِنْهُمْ مُفْطِرٌ، فَقَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ: ((اذْهَبْ إِلَيْهِمْ فَمَنْ كَانَ مِنْهُمْ مُفْطِرًا فَلْيُتِمَّ صَوْمَهُ))
It is narrated from the father of Ba’jah, Sayyiduna Abdullah (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said to him one day: Today is the day of Ashura, observe fasting on this day. A man from Banu Amr bin Awf said: O Messenger of Allah! I have left my people in such a state that some of them are fasting and some are not. The Prophet (peace and blessings be upon him) said: Go to them and tell them that whoever has not been fasting should observe fasting for the rest of the day.