Musannaf Ibn Abi Shayba 27:374

Muhammad ibn Bishr narrated to us, he said: Muhammad ibn ‘Amr narrated to us, he said: Abu Salamah narrated to us, he said: Sa’d said: "As for, by Allah, he was not the earliest of us in Islam, but I have known for what he was favored over us: he was the most ascetic of us regarding the world," meaning ‘Umar ibn al-Khattab.