Musnad Ahmad 830:96

'Abd al-Razzaq narrated to us, Ma'mar informed us, from Qatadah and more than one person, from al-Hasan, from Abu Bakrah, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Verily, the fragrance of Paradise is found from a distance of a hundred years' journey. And there is no servant who kills a person under a covenant (mu'ahadah) except that Allah forbids Paradise to him, and (forbids) its fragrance for him to find it." Abu Bakrah said: "May Allah deafen my ears if I did not hear the Prophet, peace and blessings of Allah be upon him, saying it."