Does the foster son inherit from his deceased foster mother who has no other relatives to inherit from her?

The causes of inheritance are legally defined and are three agreed-upon: marriage, kinship, and clientship (manumission). There are also disputed causes such as patronage and contractual alliance, converting to Islam at one's hands, finding a lost child, and the Islamic treasury (Bayt al-Mal). Fosterage is not a cause of inheritance. So, if a woman dies and has no heir, her wealth goes to the Muslim treasury, and her foster son does not inherit from her. Sheikh Ibn 'Uthaymeen emphasized that the fosterage connection is not among the causes of inheritance, and in this case, the inheritance devolves to the Muslim treasury.