{The sin of old covenant Israel & Judah was their worship of false gods, (instead of worshipping the LORD). This is the root-evil that they should have repented of}

Jeremiah 35.15

“I have sent also unto you all my servants the prophets, rising up early and sending them, saying, Return ye now every man from his evil way, and amend your doings, and go not after other gods to serve them, and ye shall dwell in the land which I have given to you and to your fathers: but ye have not inclined your ear, nor hearkened unto me.”

Isaiah 2.6-9

6 “Therefore thou hast forsaken thy people the house of Jacob, because they be replenished from the east, and are soothsayers like the Philistines, and they please themselves in the children of strangers.
7 Their land also is full of silver and gold, neither is there any end of their treasures; their land is also full of horses, neither is there any end of their chariots:
8 Their land also is full of idols; they worship the work of their own hands, that which their own fingers have made:
9 And the mean man boweth down, and the great man humbleth himself: therefore forgive them not.”