What is the ruling on i'tikaf (spiritual retreat) without the approval of one's mother and wife?

It is not permissible to disobey the mother by performing I'tikaf (spiritual retreat) if it is not obligatory, as obedience to parents takes precedence over supererogatory acts of worship. If one disobeys her and performs I'tikaf, he has sinned, but his I'tikaf is valid. However, if the I'tikaf is obligatory, such as a vowed I'tikaf, then the right of Allah Almighty takes precedence. As for the wife, it is permissible to perform I'tikaf without her consent, as long as it does not lead to her neglect or cause her harm.