Musannaf Ibn Abi Shayba 17:1092

Abu al-Ahwas narrated to us, from Simak, from Ikrimah, from Ibn Abbas, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "There is no *tiyarah* (superstitious belief in omens) and no *safar* (superstitious belief regarding the month of Safar)."