NASAI-KUBRA 2868:
from Ayn ʿUlamāʾukum —
[Machine] I heard the Messenger of Allah, ﷺ , say on this day, "This is the day of Ashura, and Allah has not obligated fasting on you. But I am fasting, so whoever among you wishes to fast, let him fast, and whoever does not wish to fast, let him break his fast." Abu Abdur-Rahman said, "This is an incorrect hadith, and we do not know of any of the companions of Az-Zuhri who narrated this hadith from Abu Salamah except for this. The correct narration is from Humaid bin Abdul Rahman."
الكبرى للنسائي ٢٨٦٨:
عن اين علماءكم —
سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ لِهَذَا الْيَوْمِ «هَذَا يَوْمُ عَاشُورَاءَ وَلَمْ يَكْتُبِ اللهُ عَلَيْكُمْ صِيَامَهُ وَأَنَا صَائِمٌ فَمَنْ أَحَبَّ مِنْكُمْ أَنْ يَصُومَهُ فَلْيَصُمْهُ وَمَنْ كَرِهَ فَلْيَدَعْهُ» قَالَ أَبُو عَبْدِ الرَّحْمَنِ وَهَذَا حَدِيثٌ خَطَأٌ لَا نَعْلَمُ أَنَّ أَحَدًا مِنْ أَصْحَابِ الزُّهْرِيِّ قَالَ فِي هَذَا الْحَدِيثِ عَنْ أَبِي سَلَمَةَ غَيْرَ هَذَا وَالصَّوَابُ حُمَيْدُ بْنُ عَبْدِ الرَّحْمَنِ
hadithunlocked.com