أَخْبَرَنَا يَعْلَى ، عَنْ مُحَمَّدِ بْنِ إِسْحَاق ، عَنْ نَافِعٍ ، عَنْ ابْنِ عُمَرَ ، قَالَ : قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ :" هَذَا يَوْمُ عَاشُورَاءَ، وَكَانَتْ قُرَيْشٌ تَصُومُهُ فِي الْجَاهِلِيَّةِ، فَمَنْ أَحَبَّ مِنْكُمْ أَنْ يَصُومَهُ، فَلْيَصُمْهُ، فَمَنْ أَحَبَّ مِنْكُمْ أَنْ يَتْرُكَهُ فَلْيَتْرُكْهُ ".
وَكَانَ ابْنُ عُمَرَ لَا يَصُومُهُ إِلَّا أَنْ يُوَافِقَ صِيَامَهُ

Ya’la told us, on the authority of Muhammad ibn Ishaq, on the authority of Nafi’, on the authority of Ibn Umar, he said: The Messenger of God, may God bless him and grant him peace, said: “This is the day Ashura, and the Quraysh used to fast it in pre-Islamic times, so whoever among you likes to fast it, let him fast it, and whoever among you likes should leave it. Let him leave it.”
Ibn Umar would not fast unless it coincided with his fast.