2 Kings 10:6-8

6Then he wrote to them a second letter, saying, "If you are on my side, and if you are ready to obey me, take the heads of your master's sons and come to me at Jezreel tomorrow at this time." Now the king's sons, seventy persons, were with the great men of the city, who were bringing them up.

7And as soon as the letter came to them, they took the king's sons and slaughtered them, seventy persons, and put their heads in baskets and sent them to him at Jezreel.

8When the messenger came and told him, "They have brought the heads of the king's sons," he said, "Lay them in two heaps at the entrance of the gate until the morning."