Musannaf Ibn Abi Shayba 26:179

Ibn Mahdi narrated to us, from Malik ibn Anas, from al-Zuhri, from Qabisa ibn Dhu'ayb, that Umar used to assign [a share] to the grandfather, just as the people assign to him today. I said to him: "Do you mean the opinion of Zayd ibn Thabit?" He said: "Yes."