It is narrated from Hazrat Ubayy bin Ka'b (may Allah be pleased with him) that it was the blessed practice of the Noble Prophet (peace and blessings be upon him) to observe i'tikaf during the last ten days of Ramadan. One year, the Noble Prophet (peace and blessings be upon him) was on a journey, so he could not observe i'tikaf. Therefore, when the next year came, the Noble Prophet (peace and blessings be upon him) observed i'tikaf for twenty days.