Legal Sources of Islamic Inheritance Law

".... obey Allah and obey Rasul and obey ulil amri among you. Next if you have difference of opinion, return it to Allah (Quran) and Rasul (Sunnah)...." (Quran 4:59)

Why muslims must obey ulil amri? Because ulil amri follow the law that agreed by fuqahas.

So, according to Quran (4:59), legal sources of Islamic Inheritance law are:

1. Quran
2. Sunnah Rasul
3. Ijtihad.

Quran
There are sections about inheritance:
A. the principal sections:

1. Quran (4:11): contains stipulations about share of child/children, father, and mother
2. Quran (4;12): share of widower, widow, and brother/sister
3. Quran (4:176): about kalalah (no child and no father).

B. the assistant sections:

1. Quran (4:7): man and woman have right to inherit their parent's wealth and their families's wealth
2. Quran (4:1): blood relation result in right to inherit
3. Quran (4:8): about other families, the orphans and the poor
4. Quran (4:33): about people ever swore to loyal to the deceased
5. Quran (2:180): testament (wasiat)
6. Quran (2:240): teach husband to make testament to his wife about goods

Sunnah Rasul

1. Hadist from Bukhari and Muslim : residu of inheritance especially for heir closer to deceased
2. Bukhari and Muslim: about wala' (slave's inheritance that no family)
3. Ahmad and Abu Daud: if no heir/heiress
4. Al-Jama'ah except Muslim and Nasai: muslim can not inherit from non-muslim, and non-muslim can not inherit from muslim
5. Ahmad, Malik, and Ibnu Majah: a murderer can not inherit from someone that he killed
6. Bukhari: about case that heiress are 1 daughter, 1 grand-daughter (from son) and 1 sister, Prophet Muhammad shared 1/2 to daughter, 1/6 to grand-daughter, and residu to sister
7. Ahmad: that Prophet Muhammad gave 1/6 to 2 grandmothers.

Ijtihad

1. share of hermaphrodite
2. about residu after shared to all heirs
3. share of mother.