Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions.   Wa alaikum assalam wa rahmatullahi wa barakatuh.   As to what follows:   In response to your question, we say:     The principle is that a person in i’tikaaf should always stay in the mosque except if he has to go out for a necessity.  If he goes out for unnecessary reasons like going for a walk, or going out for something which he can do without, then this undoubtedly invalidates i’tikaaf.  However, if the person goes out for a necessity like bathing, food, answering the call of nature and so on, then there is no problem if he goes out for a long or short time. However, he should not unnecessarily extend the time that he stays outside the mosque. For example if he goes out for bathing he should not extend the time and relax, because he was permitted to go out and fulfill his need, and a need should be dealt with proportionately. Thus he should hasten and go back to the mosque to perform acts of worship. I’tikaaf is a Sunnah, and if a person will it do it in the prescribed manner then why should he impose upon himself something that is difficult for him, or something that he cannot do in the manner in which it was legislated by Allah the Exalted and His Messenger (peace be upon him)