דברי הימים ב, פרק כ״ד, פסוק כ״ב

The ultimate act of ingratitude and refusal to accept correction occurs when a king executes a prophet who is the son of the very man who saved his life. Jehoiada had once rescued Joash from certain death and secured his position as king. By ignoring this immense act of kindness, Joash chose to repay good with evil [מצודת דוד, מלבי״ם]. This action was not merely a betrayal of a personal benefactor. It was a severe violation of the fundamental obligation to listen to a prophet, even when the message is harsh and difficult to hear. This duty is even more critical when the messenger serves as both a prophet and a priest [ביאור שטיינזלץ].

In his final moments, Zechariah did not remain silent, choosing instead to hand his judgment over to Heaven [מלבי״ם]. He declared that since he was being murdered innocently, with his only offense being the faithful delivery of God's message, it was right and just for God to witness the act and punish the killers [רש״י, מצודת דוד, ביאור שטיינזלץ]. This dying plea for justice did not go unanswered. The call for accountability materialized rapidly, and the prophet's death was avenged just one year after the tragic event [רש״י].