2 Chronicles 36:13
And he also rebelled against king Nebuchadnezzar, who had made him swear by God: but he stiffened his neck, and hardened his heart from turning unto the LORD God of Israel. And he also rebelled against king Nebuchadnezzar, who had made him swear by God: but he stiffened his neck, and hardened his heart from turning unto the LORD God of Israel.
Nebuchadnezzar had made Zedekiah king, and so stood as his benefactor to whom a debt of gratitude was owed. In return Zedekiah took a solemn covenant oath of allegiance to Nebuchadnezzar in the name of the Lord God of Israel. That covenant oath he renewed during a visit to Babylon. It was taken in a formal court ceremony, with Zedekiah standing before Nebuchadnezzar seated on his throne and surrounded by Babylonian officers while a scribe kept the documents, and with uplifted arm taking the vow of loyalty.
He violated that oath and stood foremost among those rapidly leading Judah to ruin, rebelling against his benefactor, against the prophets, and against God, and basely betraying every sacred trust. In the vanity of his own wisdom he broke the covenant by turning for help to Egypt, the ancient enemy of Israel's prosperity, sending ambassadors there to seek horses and many people for war.
In doing so he utterly forsook the counsels of the Lord given through the prophets and refused to humble himself before Jeremiah speaking from the mouth of the Lord, stiffening his neck and hardening his heart from turning to the Lord God of Israel, which was evil in the sight of the Lord. Keeping the oath would have honored the name of the living God before many who were watching the conduct of those claiming to reverence God. By breaking it he lost the high privilege of bringing honor to God's name.