Abu Wa'il Shaqiq bin Salamah said: I went to Ibn Mas'ud (may Allah be pleased with him) on the day of Ashura while he was eating fresh dates. He said: "This is the day of Ashura, a day whose fasting we were commanded before (the fasting of) Ramadan was revealed."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10400