The meaning of ‘I’tikaaf’ is to seclude oneself in the Mosque, with the express intention (Niyyat)of ‘I’tikaaf’. According to the Hanafi school of thought, this may be of three different types:
a) Waajib I’tikaaf (Obligatory I’tikaaf)
I’tikaaf becomes compulsory when a person makes it obligatory upon himself. For example, when a person makes a vow to Allah that if Allah fulfils a certain wish of his, he shall perform so many days ‘I’tikaaf’, in this case, the moment his wish is fulfilled, the I’tikaaf becomes compulsory. Or a person may just make an unconditional vow, whereby he makes I’tikaaf Waajib upon himself for a certain number of days; this becomes obligatory for him from that moment onwards.