Musannaf Ibn Abi Shayba 27:372

Muhammad ibn Marwan narrated to us, from Yunus, who said: Al-Hasan would sometimes mention Umar and say: "By Allah, he was not the first of them in Islam, nor was he the one who spent the most in the way of Allah, but he surpassed the people through asceticism in the world and firmness in the command of Allah, and he did not fear the blame of any critic for the sake of Allah."