I say, and with God's help: There are three types of i'tikaf: 1. Obligatory: This is the i'tikaf of a vow; because he has made it obligatory upon himself, and fasting is a condition for its validity. If he vows for certain days, he must observe them along with their nights consecutively. 2. Sunnah: This is during the last ten days of Ramadan. 3. Recommended: This is throughout the rest of the year, and fasting is not a condition for it; it is permissible even for a moment in a congregational mosque, and God knows best.