They stiffened their neck and did more evil than their fathers (v. 26).
Israel did not listen to the voice of Jehovah their God and did not take correction. Truth perished and was cut off from their mouth (v. 28). They had given up the truth and no longer spoke about it.
Israel did that which was evil in Jehovah's sight. They set up their abominations in the house which was called by His name, to defile it (v. 30). This means that they set up idols in the house of Jehovah.
Israel even went so far as to build the high places of Topheth to burn their sons and daughters in the fire (v. 31).
Israel turned away in perpetual apostasy. They held fast to deceit and refused to turn back (8:5). Israel's apostasy was not temporary—it was perpetual.
They did not speak rightly (v. 6a), and no one repented of his wickedness, saying, "What have I done?" (v. 6b). Rather, everyone turned to his own course, like a horse rushing headlong into battle (v. 6c).
Israel did not know the ordinance (of the law) of Jehovah. They were unlike the stork, which knows its own appointed times, and the turtledove, the swallow, and the crane, which keep the time of their coming (v. 7). These birds knew the time of their coming and going, but Israel was not knowledgeable concerning the times of God's intention.