4:23Forbidden for you are your mothers, your daughters, your sisters, your paternal aunts, your maternal aunts, your brother's daughters, your sister's daughters, your foster-mothers who nursed you, your sisters through nursing, your wives' mothers, and your stepdaughters in your guardianship—born of wives you have gone into—but if you have not gone into them, there is no blame on you. And the wives of your genetic sons, and marrying two sisters simultaneously. Except what is past. God is Oft-Forgiving, Most Merciful.

4:176They ask you for a ruling. Say, “God gives you a ruling concerning the person who has neither parents nor children.” If a man dies, and leaves no children, and he had a sister, she receives one-half of what he leaves. And he inherits from her if she leaves no children. But if there are two sisters, they receive two-thirds of what he leaves. If the siblings are men and women, the male receives the share of two females.” God makes things clear for you, lest you err. God is Aware of everything.