Complete Fiqh of Knowledge

The law of inheritance in Islam is based on texts in the Koran as follows

And for you (husbands) half of the wealth your wives leave, if they have no children. If your wives have children, then you get a quarter of their abandoned property to have their wills or (and) paid for their debt. Wives earn a quarter of the property you leave if you have no children. If you have children, then wives get an eighth of the property you leave after being filled with the will you make or (and) after being paid your debts. If a person dies, both men and women who do not abandon the father and do not abandon the child, but have a brother (a thousand) or a sister (one thousand), then for each of the two siblings is sixth property. But if the brothers are more than one, then they are allied in that one third, after being fulfilled by his will or after being paid his debt by not harming (to heirs). (Allah) establishes that which is really from Allah, and Allah is All-Knowing, Most Forbearing (verse 12)