Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) asked the Messenger of Allah (peace and blessings be upon him) while he (peace and blessings be upon him) was at al-Ji'ranah, after returning; he said: "O Messenger of Allah (peace and blessings be upon him)! I vowed in the Jahiliyyah that I would observe i'tikaf for one day in al-Masjid al-Haram; so what is your view?" He (peace and blessings be upon him) said: "Go and observe i'tikaf for one day." The Messenger of Allah (peace and blessings be upon him) had given him a slave girl from the one-fifth. When the Messenger of Allah (peace and blessings be upon him) freed the people's captives, Umar (may Allah be pleased with him) said: "O Abdullah (may Allah be pleased with him)! Go and free that slave girl too."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12937