Albert Barnes Commentary 2 Kings 10:6

"Then he wrote a letter the second time to them, saying, If ye be on my side, and if ye will hearken unto my voice, take ye the heads of the men your master`s sons, and come to me to Jezreel by to-morrow this time. Now the king`s sons, being seventy persons, were with the great men of the city, who brought them up." — 2 Kings 10:6 (ASV)

In the East, the heads of rivals, pretenders, and other hostile persons are commonly struck off and brought to the chief ruler as proof that his enemies have ceased to live. In Assyrian sculptures, we constantly see soldiers carrying heads from place to place—not in baskets, however, but in their hands, holding the head by the hair.