Musnad Ahmad 33:830

Hassan ibn al-Rabi' narrated to us, Ibn al-Mubarak narrated to us, from 'Utbah ibn Abi Hakim, from Husayn, from Abu al-Musabbih, from Jabir ibn Abdullah, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Whoever’s feet become dusty in the way of Allah, then they are forbidden to the Fire."