Musnad Ahmad 1080:1

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from al-Zuhri, from Ibn al-Musayyib, from his father: That the Prophet, peace and blessings of Allah be upon him, said to his grandfather, the grandfather of Sa'id: "What is your name?" He said: "Hazn (Rough/Grief)." The Prophet, peace and blessings of Allah be upon him, said: "Rather, you are Sahl (Easy/Smooth)." He said: "I will not change a name that my father named me." Ibn al-Musayyib said: "So roughness (huzunah) has not ceased to be among us ever since."