2 Samuel 10:4

Hanun … shaved off the one half of their beards. To an Oriental the beard was the mark of his being a free man, and to cut it off on one side was not merely an insult to David's ambassadors, but the treating them like slaves. Moreover, as only the priests wore underclothing, and as the ordinary dress of men consisted of a tunic and a loose flowing robe thrown over it, the cutting of this robe short up to the hip was a vile and abominable affront. Of course, Hanun intended this as a challenge to war, whereas David had meant peace and friendship.