The Ruling on Using a Woman as a Dowry for the Marriage of Another Woman

Question :

A person proposed to my sister, but he informed me that his family would not agree to his marriage to my sister unless I married his sister. However, I did not pay a dowry to my bride, but we agreed upon an advance payment and the payment of the remainder. I prepared my house and my sister, while the other person prepared his sister and his house. What is the ruling on this contract, and is the marriage considered Ash-Shigar?

Answer:

This contract is unlike Nikah Ash-Shighar, because Nikah Ash-Shighar is when (a man) says: "I will not marry you to my daughter unless you marry me to your daughter."

The question asked by the questioner is contrary to Nikah Ash- Shighar. But having said this, I say: If this occurred by way of exchange, meaning that each of the two women is a dowry for the other, then that is not permissible. Allah, Most High has made permissibility dependent upon the giving of wealth, and you and the other man did not seek them by your property. Instead, each of you made the woman a dowry for the other and this is unlawful, and it is invalid. However, if you both fixed a dowry, some of the scholars say regarding Nikah Ash-Shighar: If they both fixed a full dowry, and each of the women accepted the man who married her, then the marriage in that case is valid. My verdict to you is to return to the Court in your area, and if they confirm the first marriage, then it is as the court sees it, but if they do not confirm it and the Islamic Law Judge considers that the marriage must be repeated, then repeat the marriage.

Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 5 Pages 420-421