Some mosques have a room used as a storage area or the like; what is the ruling on performing i'tikaf (spiritual retreat in the mosque) in it, and what is the stronger opinion regarding the beginning and end of i'tikaf?

The questioner : His EminenceThe Shaykh : Some mosques and congregational mosques have rooms attached to them that are used as libraries, or some are empty, and some are storage areas. Are these rooms within the boundary of the mosque? Is it valid to perform i'tikaf in them? Are they considered equivalent to the tent that the Prophet (peace and blessings be upon him) ordered to be set up when he intended to perform i'tikaf? And what is the stronger opinion regarding the beginning and end of i'tikaf? May Allah reward you with good.

The Shaykh : A room that is inside the boundary of the mosque is part of the mosque, whether it is a library, a storage area, or something else; its ruling is the ruling of the mosque. If a person enters it, he must pray two rak'ahs (units of prayer) before sitting down. If he performs i'tikaf in it, it is valid. Buying and selling are not permissible in it. The important point is that it has the rulings of the mosque.
As for i'tikaf, the correct opinion is that the person enters his state of i'tikaf before the sun sets on the night of the twentieth, meaning he anticipates the night of the twenty-first before the sun sets on the day of the twentieth, so he anticipates the night of the twenty-first. The i'tikaf ends with the setting of the sun on the last day of Ramadan.

The questioner : May Allah reward you with good.