It is narrated from Sayyiduna Zayd bin Thabit (may Allah be pleased with him) that he said: "The day of Ashura is not the day that people commonly speak of; rather, it was the day on which the Ka'bah was covered with its cloth and the Abyssinians would dance in the presence of the Messenger of Allah (peace and blessings be upon him), and this day used to rotate through the year." People used to ask a certain Jew about it; when that Jew died, the people came to Zayd bin Thabit (may Allah be pleased with him) and began to ask him.
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4857