The condition of being male is not required for the validity of i'tikaf (spiritual retreat). A woman can perform i'tikaf with her husband's permission if she has a husband, as she is among those who are eligible for worship. The only hindrance is the husband's right. If permission is granted, the hindrance is removed. Therefore, if a woman vows to perform i'tikaf, her husband has the right to prevent her. If she is divorced, she must fulfill her vow because the husband has ownership of the benefit from her. In i'tikaf, he is deferring his right to benefit, so he has the right to prevent her as long as she is under his ownership. If she is divorced from him, she is obligated to fulfill her vow, and the vow is valid from her since she is among those eligible, but she was prevented due to her husband's right. Once his right is removed by divorce, the hindrance is lifted, and she must fulfill her vow. See: Al-Badai 2: 109.