Definition of Shighar Marriage and Its Ruling

Question:
His other question says: What is shighar marriage? And what are the defective conditions that invalidate the marriage contract?

Answer:
Shighar marriage is making a woman in exchange for a woman; he marries his daughter on the condition that the other marries his daughter, with no mahr (bridal gift) between them, no mahr between them. This is invalid. This is shighar by consensus. If there is a mahr between them, each having a mahr like the other’s, this is a matter of scholarly disagreement. The majority hold that the contract is valid, because [it is] present and there is no harm to either of them.
The second opinion is that it falls under shighar as well, because it is not free from harming the woman; even if there is a mahr, it is not free from harming her. And this is the stronger position, and Allah knows best. Yes, shighar is making a woman in exchange for a woman, even if there is a mahr between them. Yes.