Musannaf Ibn Abi Shayba 26:183

Shababa narrated to us, from Yunus bin Abi Ishaq, from Abi Ishaq, from ‘Amr bin Maymun, from Ma’qil bin Yasar al-Muzani, who said: I heard the Messenger of Allah (peace and blessings of Allah be upon him) when an obligatory share (inheritance case) was brought to him in which there was a grandfather, and he gave him a third or a sixth.