What is the ruling on shighar marriage with the payment of the mahr?

Question:
What is the ruling on shighar marriage where the mahr is paid to each of the two parties, but with the condition that each marries the other, and if one party refuses, the other party will also refuse?

Answer:
Shighar marriage is what people call "exchange." It is not permissible and is invalid. The Prophet (peace and blessings be upon him) prohibited it in hadiths and said: This is the shighar known by many people as "exchange," or exchange marriage, and it is not permissible. The Prophet (peace and blessings be upon him) prohibited it because of the disputes and litigation it entails, and because it conditions a woman as the mahr for another woman.
In their view, the mahr has no value; the intention is the exchange of a woman for a woman. Therefore, the mahr does not make it permissible. This is the correct view. There is disagreement among the scholars; some said that her customary mahr is sufficient, but this is an incorrect opinion that contradicts the authentic hadiths. The intention is not the absence of mahr, but rather the condition that this woman is the mahr for that woman. This leads to forcing women and oppressing women, and it leads to prolonged disputes. Whenever something happens between one man and his wife, something happens between the other man and his wife as well, because each woman is tied to the other. This results in corruption and evil that is not hidden from anyone. The Prophet (peace and blessings be upon him) prohibited shighar and did not say "except if it is accompanied by a mahr" or "if it is with a mahr."
As for what is narrated in the hadith of Ibn 'Umar ("and there was no mahr between them"), this is the statement of one of the narrators, not the statement of the Prophet (peace and blessings be upon him). Rather, it is the statement of Nafi', who is the narrator from Ibn 'Umar. What the Prophet (peace and blessings be upon him) actually said is what was mentioned earlier, namely his saying: This is what came in the hadith of Abu Hurayrah in Sahih Muslim. It is also established in the hadith of Mu'awiyah (may Allah be pleased with him) that it was reported to him that two men from Quraysh in Medina had married each other's daughters in a shighar marriage, and they had named a mahr between them. Mu'awiyah (may Allah be pleased with him) wrote to the governor of Medina and ordered him to separate them, saying: "This is the shighar that the Prophet (peace and blessings be upon him) prohibited." He did not pay attention to the mahr they mentioned because it was not the intention; the intention is the exchange of a woman for a woman. This is the purpose of shighar.