His statement, “If it is invalid but she has taken possession of it, it remains hers”: an example is where he gives her wine as the bridal gift, and wine is lawful according to their religion. We say: if she has already taken possession of it, it remains hers, because they regard wine as property, and she has taken possession of it; therefore, we do not interfere.
His statement, “If she has not taken possession of it and no bridal gift was stipulated, she is assigned the customary bridal gift”: that is, if she has not taken possession of the bridal gift and none was stipulated, then she is entitled to the customary bridal gift. This is the rule in Islamic law: whenever a bridal gift has not been stipulated, she is entitled to the customary bridal gift.
His statement, “and no bridal gift was stipulated”: if one was stipulated, she receives the stipulated amount if it is valid. But if it is invalid and she has not taken possession of it, its value is assessed. How much would this wine be worth to someone who considers it lawful? If they say, for example, one hundred riyals, we say: she is entitled to one hundred riyals. We cannot give her the wine, because wine is forbidden; rather, she is given its value (1).