The purpose of i'tikaf is to reduce one's dealings with the world to a minimum so that a person is left alone with themselves; to reflect on the purpose of their creation and the duties they carry; to keep vigil on the Night of Decree; and, through greater worship and supplication, to hope for forgiveness and draw nearer to God.
In Islamic literature, i'tikaf means “to withdraw into seclusion in a mosque, intending to seek the pleasure of God, and observing certain rules.” The hadith sources relate that after the migration to Medina the Prophet ﷺ withdrew into i'tikaf during the last ten days of every Ramadan, and that his wives generally observed i'tikaf with him. (Muslim, “I'tikāf”, 3; Tirmidhī, “Ṣawm”, 80)
According to ʿĀ'isha (may God be pleased with her), when the last ten days of Ramadan began the Messenger of God ﷺ would keep vigil at night, wake his family for worship, devote himself to worship more intensely than at any other time, and recommend the same to the Muslims. (Muslim, “I'tikāf”, 7)
As a form of worship, i'tikaf has been known since the time of Abraham (2/al-Baqarah, 125). Confirmed by the Qur'an, it occupies an important place in the life of the Prophet ﷺ, who is known to have observed it every year in Medina except for one. (Tirmidhī, “Ṣawm”, 79)
Known even to pre-Islamic Meccan society, i'tikaf acquired the character of a sunnah through the Prophet's practice ﷺ. He would enter i'tikaf in the Prophet's Mosque — most often during the last ten days of Ramadan — spending every hour of the day there. A tent was pitched for him inside the mosque for this purpose, and he is known not to have left except for necessities. (Muslim, “I'tikāf”, 79; Tirmidhī, “Ṣawm”, 1-6; Abū Dāwūd, “Ṣawm”, 77-78)
Entering i'tikaf is a more effective way of guarding the self against what is forbidden, and it increases both the opportunity and the hope of keeping vigil on the Night of Decree, expected within the last ten days of Ramadan. For the Muslim who cannot find time for themselves amid the density of modern life, i'tikaf is a rare opening: a way to take account of the year gone by, to plan the future more fruitfully, and to draw more deeply on the spiritual climate of Ramadan.