Musnad Abu Ya'la al-Mawsili 110:278

Abu Jahl said, "If I see Muhammad praying at the Kaaba, I will certainly come to him until I step on his neck." The Messenger of Allah (peace be upon him) said, "If he had done that, the angels would have seized him openly. And if the Jews had wished for death, they would have died and seen their places in the Fire. And if those who engaged in *mubahalah* (mutual imprecation) with the Messenger of Allah (peace be upon him) had gone out, they would have returned finding neither family nor wealth."