Musannaf Ibn Abi Shayba 34:55

'Abd al-A'la narrated to us, from Dawud, from Shahr ibn Hawshab, from 'Abd al-Rahman ibn Ghanam, who said: The first grandfather to inherit in Islam was 'Umar ibn al-Khattab. He wanted to take the entire wealth, so I said, "O Commander of the Faithful, they are a tree below you," meaning his children's children.