Musannaf Ibn Abi Shayba 26:61

Yahya ibn Zakariyya narrated to us, from Isra'il, from Mansur, from Ibrahim, regarding a woman who left behind her two maternal half-brothers, one of whom was her paternal cousin. Ali and Zayd said: "The third is between them, and what remains is for the paternal cousin." Ibn Mas'ud said: "The wealth is between them [the two brothers]." Abu Bakr said: "So this, according to the statement of Ali and Zayd, is out of three shares, and according to the statement of Ibn Mas'ud, it is out of two shares."