2 Kings 10:6-7

6Then Jehu wrote them a second letter, saying, “If you are on my side and will obey me, take the heads of your master’s sons and come to me in Jezreel by this time tomorrow.” Now the royal princes, seventy of them, were with the leading men of the city, who were rearing them.

7When the letter arrived, these men took the princes and slaughtered all seventy of them. They put their heads in baskets and sent them to Jehu in Jezreel.