6Then Jehu wrote them a second letter and said: “If you are on my side, and if you will obey me, then bring the heads of your master’s sons to me at Jezreel by this time tomorrow.” Now the sons of the king, seventy in all, were being brought up by the leading men of the city.
7And when the letter arrived, they took the sons of the king and slaughtered all seventy of them. They put their heads in baskets and sent them to Jehu at Jezreel.
— 2 Kings 10:6-7