[4:33] To each We have appointed heirs (mawālī) of that which parents and kinsmen leave and to those to whom your right hands were pledged. So give them their share. God is ever Witness over everything.
In the beginning of Islam, He appointed the head of the family in the contractual arrangements determining inheritance, but then the decree of inheritance was abrogated while the decree of respect remained. If this was the manner of making contracts between men, what do you think of making contracts with God? God Most High said: men who are true to the covenant they made with God [33:23]. They have recited:
Verily those who have died
to the religion of whims
have found the decree of death
a sweet watering place.