Is a second marriage considered to nullify the first marriage if the first marriage contract stipulated that the husband was not to marry another woman while married to his first wife?

The preponderant opinion is that it is permissible for a woman to stipulate to her husband that he should not marry another woman, and this is a binding condition according to the Hanbalis. It does not mean that the marriage is null and void if the husband violates the condition; rather, the wife has the right to annul the marriage. If she agrees to remain married, then the marriage is valid. However, this condition, if made after the marriage contract and consummation, is not binding according to the Hanbalis, for conditions are only binding if they occur before or at the time of the contract. As for conditions made after the contract has become binding, they are not binding.