Is it permissible to marry a relative and postpone procreation until the necessary medical tests are conducted, knowing that the engagement cannot be annulled, and if the test results are unfavorable, is it permissible to refrain from procreation?

Allah has legislated marriage for great benefits, and there is no Sharia text that prohibits marriage between relatives. Rather, there are texts indicating its permissibility, such as the Prophet's (peace be upon him) marriage to his female cousin, and his giving his daughter Fatimah in marriage to Ali ibn Abi Talib.

Therefore, the statement that marriage between relatives causes diseases is not entirely accurate, as the occurrence of diseases is rare and not prevalent. If medical analyses prove a risk in a specific case, then there is no harm in refraining from marrying that particular relative.

The default rule for marriage between relatives is permissibility. If there is a specific issue or a particular hereditary disease that is feared, modern science has reached what the ancients did not, and reliable medical standards can be applied.

One must rely on Allah and have a good opinion of Him. Marriage to relatives should not be prohibited out of fear of imagined diseases, for disability occurs by Allah's decree and destiny, and not because of marrying female relatives.