Musnad Ahmad 712:0

Narrated to us by Muhammad ibn Ja’far, who said: Narrated to us Shu’bah, from Qatadah, who said: I heard Nasr ibn ‘Asim narrating from Furat ibn Hayyan al-‘Ijli, that the Prophet (ﷺ) said: "Whoever meets me, let him not meet me except with a pure heart." And he said: "And whoever meets me while he is a believer, then he is safe."