Charles Ellicott Commentary 2 Chronicles 12:1

"And it came to pass, when the kingdom of Rehoboam was established, and he was strong, that he forsook the law of Jehovah, and all Israel with him." — 2 Chronicles 12:1 (ASV)

When Rehoboam had established the kingdom. —Rather, when Rehoboam’s kingdom had been established. The construction is impersonal: when one had established Rehoboam’s kingdom. The narrative is resumed from 2 Chronicles 11:17.

And had strengthened himself. — And when he had become strong (hezqâh, an infinitive, used again at 2 Chronicles 26:16; Daniel 11:2, and nowhere else).

He forsook the law of the Lord — i.e., lapsed into idolatry. (See 1 Kings 14:22–24, where the offence is more precisely described.)

All Israel. —The southern kingdom being regarded as the true Israel. (Compare 2 Chronicles 12:6.)