faqih-5600Vol. 4, p. 262
لِلْأُمِّ الثُّلُثُ وَ لِلْأَبِ الثُّلُثَانِ.
Hadith.5611 - Al-Hasan ibn Mahbub narrated from Ali ibn Ri'ab from Zurara from Abu Jafar Imam Muhammad ibn Ali Al-Baqir (as) regarding a man who passed away and left behind his parents. Imam (as) said: "The mother receives one-third, and the father receives two-thirds."