Fœnum habet in cornu, longe fuge

Fly from that man, he has hay on his horns. This is said of persons of morose, quarrelsome, and malevolent dispositions, with whom it is dangerous to associate; alluding to the custom of fixing whisps of hay to the horns of vicious oxen. «Hic est niger, hunc tu, Romane, caveto». This is a dangerous fellow, beware of him.