عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُ أَنَّهُ قَالَ فِي عَاشُورَاءَ: صَامَهُ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ وَأَمَرَ بِصِيَامِهِ فَلَمَّا فُرِضَ رَمَضَانُ تَرَكَ، فَكَانَ عَبْدُ اللَّهِ لَا يَصُومُهُ إِلَّا أَنْ يَأْتِي عَلَى صَوْمِهِ
Sayyiduna Abdullah bin Umar (may Allah be pleased with him) said regarding the Day of Ashura: The Messenger of Allah (peace and blessings be upon him) himself fasted on this day and also ordered fasting on it, but when the month of Ramadan was made obligatory, fasting on this day was abandoned. Thus, Sayyiduna Ibn Umar (may Allah be pleased with him) would not fast on this day, except if it coincided with a day on which he would customarily fast.