The World Federation One Stop Fiqh

Ruling 1767

It is not permitted to change from one iʿtikāf to another, whether both iʿtikāfs happen to be obligatory, like when a person has made one of them obligatory on account of a vow and the other on account of an oath; or, both are recommended; or, one is obligatory and the other recommended; or, one is to be performed for himself and the other on behalf of someone else (niyābah) or he is being hired to perform it for someone else; or, both are to be performed on behalf of someone else.