From whom is Iila' valid regarding the husband?

Primary text

The Iila' is valid from every mature husband capable of sexual intercourse. The pen is lifted from the boy and the insane person concerning Iila', and it is a vow upon which a penalty or right depends, so it is not established from them, similar to a vow (Nathr). If the husband is incapable of intercourse due to a temporary condition whose removal is hoped for, such as illness or imprisonment, his Iila' is valid because he is capable of intercourse, making his abstinence via an oath valid. However, if the incapacity is due to an irreversible condition, such as being a eunuch (Jubb) or paralyzed, his Iila' is not valid because it is an oath concerning the abandonment of the impossible, which is not established, just as if he swore not to turn stones into gold. Furthermore, Iila' is an oath preventing intercourse, but he is already prevented from it by necessity, and his oath does not harm the woman.