Musannaf Ibn Abi Shayba 26:162

Ibn Fudayl narrated to us, from Bassam, from Fudayl, from Ibrahim, regarding a woman who left behind her maternal sister and her mother, and she had no agnates ('asaba). In the judgment of Abdullah, her maternal sister receives one-sixth, and her mother receives five-sixths. Zayd judged regarding it that her maternal sister receives one-sixth, her mother receives one-third, and the remainder is placed in the public treasury (Bayt al-Mal). Ali judged regarding it that they both receive the wealth according to the proportion of what they inherited, so he gave the maternal sister one-third and the mother two-thirds. Abu Bakr said: So this, according to the opinion of Ali, is out of three shares, and according to the opinion of Abdullah and Zayd, it is out of six.