Musannaf Ibn Abi Shayba 33:994

Muhammad ibn Fudayl narrated to us, from ‘Asim, who said: I never heard al-Hasan recite a line of poetry except for this line: "He who dies and finds rest is not the dead; rather, the dead is the dead among the living." Then he said: "By Allah, he spoke the truth. For indeed, a person may be alive while his heart is dead."