What is the ruling on the condition that the prospective bride insists her fiancé agree to, that he never marry another woman, knowing that she suffers from a disease that may cause her infertility?

It is desirable to marry a fertile woman, due to the hadith: "Marry the affectionate, fertile woman, for I will boast of your numbers before the Prophets on the Day of Resurrection." Accordingly, there is no harm in marrying a barren woman, but it is disliked in a way that does not reach the level of prohibition (makruh tanzihi). A woman may stipulate that her husband not marry another woman in addition to her. In this case, the man has the choice between accepting the condition or marrying someone else who can bear him children. A barren woman who will not conceive is advised to waive this condition to facilitate her marriage.