Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "If I remain alive till the next year, I will also fast on the ninth of Muharram, so that the risk of missing the fast of the Day of Ashura is eliminated."