Musnad Ahmad 28:257

Ishaq ibn Isa narrated to us, Abd al-Rahman ibn Abi al-Zinad narrated to us, from Abd al-Rahman ibn al-Harith, from Amr ibn Shu'ayb, from his father, from his grandfather, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "He is not of us who does not show mercy to our young, and recognize the right of our elder."