Musannaf Ibn Abi Shayba 26:198

Waki’ narrated to us, from Isra’il, from Jabir, from ‘Amir, from Masruq, who said: Ibn Mas’ud used to not increase the grandfather’s share beyond one-sixth along with the brothers. He said: So I said to him, "I witnessed ‘Umar ibn al-Khattab give him one-third along with the brothers." So he gave him one-third.