Narrated Ibn Abbas: (In the Pre-Islamic Period) the children used to inherit all the property but the parents used to inherit only through a will. So Allah cancelled that which He liked to cancel and decreed that the share of a son was to be twice the share of a daughter, and for the parents one-sixth for each one of them, or one third, and for the wife one-eighth or one-fourth, and for the husband one-half, or one-fourth.

Sahih Al-Bukhari – Book 60 Hadith 102