What does 2 Kings 10:6 mean?

Jehu wrote back, If you’re really on my side and ready to obey me, bring me the heads of your master’s sons by this time tomorrow at Jezreel. The king’s sons were with the city’s leaders, who were raising them. 2 Kings 10:6 - Modern Text Bible

(Jehu demands proof of their loyalty: they must kill all of Ahab’s sons and bring their heads to him. This is a brutal purge to end Ahab’s line.)