Musnad Ahmad 30:2721

Hajjaj narrated to us, he said: Layth narrated to us, he said: Uqayl narrated to me, from Ibn Shihab, from Ubayd Allah ibn Abd Allah ibn Utbah, from Abu Hurayrah, from the Messenger of Allah, may Allah bless him and grant him peace, that he said: "There is no *tiyarah* (evil omen), and the best of it is *al-fa'l* (a good omen)." It was said: "O Messenger of Allah, and what is *al-fa'l*?" He said: "A righteous word that one of you hears."