The Prophet (may Allah's peace and blessings be upon him) used to observe I‘tikāf [spiritual retirement in the mosque] during each Ramadan for ten days. The year in which he died, he observed I‘tikāf for twenty days.
Abu Hurayrah (may Allah be pleased with him) reported: The Prophet (may Allah's peace and blessings be upon him) used to observe I‘tikāf during each Ramadan for ten days. The year in which he died, he observed I‘tikāf for twenty days.

