What is the ruling on the marriage of a man or a woman if one of them carries genetic diseases that could harm the children, and should they not marry?

If a trusted physician states that a hereditary disease in one of the spouses will be transmitted to the children, then there is no impediment to foregoing marriage, for marriage is not obligatory unless its omission is feared to lead to falling into indecency.

The couple can marry while abstaining from procreation through coitus interruptus or similar methods that do not permanently prevent conception. They are not obligated to abandon marriage or procreation, for the occurrence of diseases and procreation are matters of the unseen.

Whoever experiences a disease, whether themselves or their children, should seek reward from Allah, for the believer is rewarded for every affliction that befalls them, even a thorn that pricks them. The Prophet, peace and blessings be upon him, said: "No misfortune befalls a Muslim but Allah Almighty expiates some of his sins because of it, even a thorn that pricks him." If it is known after conception that the fetus has a deformity, then aborting it is forbidden.