Musnad Ahmad 25:1277

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Sulayman, from Mujahid, from Ibn ‘Abbas: That he was at the Stone (the Black Stone), and he had a curved staff with which he would strike the Stone, and he would kiss it. He said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "O you who have believed, fear Allah as He should be feared and do not die except as Muslims [Al-Imran: 102]. If a drop of Zaqqum (bitter tree of Hell) were to drip onto the earth, it would corrupt the livelihood of the people of the world. So how would it be for the one whose food it is, and he has no other food?"