It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the people of Jahiliyyah used to fast on the tenth of Muharram. When the command for fasting in the month of Ramadan was revealed, the people asked the Prophet (peace and blessings be upon him) about its ruling. The Prophet (peace and blessings be upon him) said: "It is one of the days of Allah; whoever wishes may fast, and whoever wishes may leave it."