من لا يحضره الفقيه, volume 2, page 184

Hadith.2086 - It is narrated by Al-Halabi from Abu Abdullah (as) that he said: "There is no valid i'tikaf (spiritual retreat) except with fasting and in a congregational mosque."

Translation: Bab Ul Qaim Publications — attributed by Thaqalayn·The Arabic above is the original.

Hadith.2087 - It is narrated: "When the last ten nights of Month of Ramadan arrived, the Messenger of Allah (swt) (peace and blessings be upon him and his family) would perform i'tikaf in the mosque. A tent made of hair would be set up for him, he would tighten his waist wrap, and he would fold up his bedding." Some people said he would also avoid the company of women. Regarding this, Abu Abdullah (as) said: "As for avoiding women, no."

Translation: Bab Ul Qaim Publications — attributed by Thaqalayn·The Arabic above is the original.

Hadith.2089 - Al-Hasan ibn Mahbub narrated from Umar ibn Yazid, who said: "I asked Abu Abdullah (as): 'What do you say about performing i'tikaf in Baghdad in some of its mosques?' Imam (as) replied: 'Do not perform i'tikaf except in a congregational mosque where a just Imam has led the congregation in prayer. There is no harm in performing i'tikaf in the mosque of Kufa, the mosque of Basra, the mosque of Medina, and the mosque of Mecca.'"

Translation: Bab Ul Qaim Publications — attributed by Thaqalayn·The Arabic above is the original.