2 Kings 10:6-7

Then Jehu wrote a second letter: If you are on my side and are willing to follow my orders, here’s what you do: Decapitate the sons of your master and bring the heads to me by this time tomorrow in Jezreel. The king’s sons numbered seventy. The leaders of the city had taken responsibility for them. When they got the letter, they took the king’s sons and killed all seventy. Then they put the heads in baskets and sent them to Jehu in Jezreel.