Musnad Ahmad 28:566

Hassan—meaning al-Ashyab—narrated to us, Ibn Lahi'ah narrated to us, Darraj narrated to us, from Abd al-Rahman ibn Jubayr, from Abdullah ibn Amr, from the Messenger of Allah (may Allah bless him and grant him peace), that he said: "For them are glad tidings in the worldly life" [Yunus: 64]. He said: "The righteous vision, the believer is given glad tidings by it; it is a part of forty-nine parts of prophethood. So whoever sees that, let him tell of it. And whoever sees other than that, it is only from Satan to grieve him, so let him spit to his left three times, and let him remain silent, and let him not tell it to anyone."