The Shighaar marriage
25-2-2008 | IslamWeb
Question:
is it right for a man to married another man's sister and in return the latter man also married the first man's sister at the same time ? { ie you marry my sister and I marry your sister}
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
There are many types of marriages when a man marries off the girl who is under his guardianship to another in return for the latter to marry off the girl under his guardianship back to him. We will mention these different types and their respective rulings in brief.
First Type: Both men agree to renounce the dowry of each woman.
Second Type: Considering the sexual enjoinment with each woman [that happens by getting married to them] as a dowry for these women.
Third Type: Not defining any dowry at all.
These three types of marriages are forbidden because both parties agree to renounce the dowry of each bride. [This is called Shighaar marriage (exchanged marriage without dowry)] If marriage takes place according to one of the above three types, then the marriage is void and it must be invalidated either before or after consummating the marriage.
Fourth Type: Defining an exact amount of dowry for one of the brides but not for the other. This type of marriage is void as well. The marriage contract with a woman whose exact amount of dowry is not defined must be invalidated either before or after consummating the marriage. If the marriage is consummated, the wife is entitled for a dowry of women at the same social status like her. As regards the wife whose exact amount of dowry is defined, then her marriage contract must be invalidated before the consummation of marriage, and if the marriage has already been consummated, the marriage contract is valid and –in this case –she is entitled to the highest amount of dowry of the following:
a) Her defined dowry.
b) The dowry of women of the same social status like her.
Fifth Type: Defining an exact amount of dowry for each one of them; this is a valid marriage according to the view of the majority of the scholars 
but some other scholars stated that even this type of marriage is void.
Therefore, it is not permissible to resort to such types of controversial marriages, as this causes harm to the brides, and this is putting the interests of the husbands and their desires in priority over the women who are under their guardianship. This is nothing but betraying the trust. Rather, each wife should have her separate and independent marriage contract in a way to fulfil her interest as confirmed in the Sharee’ah.