Musnad Ahmad 25:1624

'Abd al-Razzaq narrated to us, Ma'mar informed us, from 'Abd al-Karim, from 'Ikrimah, who said: Ibn 'Abbas said: Abu Jahl said: "If I see Muhammad praying at the Ka'bah, I will certainly step on his neck." This reached the Prophet, peace and blessings of Allah be upon him, and he said: "If he were to do it, the angels would seize him openly."