Musannaf Ibn Abi Shayba 3:2335

Waki’ narrated to us, from Kahmas ibn al-Hasan, from Ibn Buraydah, who said: It used to be said: Four things are from coarseness (jafa’): that you wipe your forehead before you finish [the prayer], or that you urinate while standing, or that you hear the caller [to prayer] and do not answer him, or that you blow [air from your mouth] during your prostration.