Musnad Ahmad 30:791

Yazid narrated to us, Muhammad—meaning Ibn Ishaq—informed us, from Salih ibn Ibrahim, from Abd al-Rahman al-A'raj, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Do not call the grape vine 'al-karm' (the generous/noble), for indeed, the 'karm' (generous/noble) is the believing man."