In the thirty and first year of Asa king of Judah began Omri to reign over Israel, twelve years: six years reigned he in Tirzah.
Solomon observes (Pro 28:2) that for the transgression of a land many were the princes thereof (so it was here in Israel), but by a man of understanding the state thereof shall be prolonged - so it was with Judah at the same time under Asa. When men forsake God they are out of the way of rest and establishment.
Commenting on 1 Kings 16:15-28
And in the thirty fifth year of Asa king of Judah began Ahab the son of Omri to reign over Israel,.... At the latter end of it, the same year his father died, see Kg1 16:23. and Ahab the son of Omri reigned over Israel in Samaria twenty two years; the same number of years Jeroboam did, Kg1 14:20.
OMRI BUILDS SAMARIA. (Kg1 16:23-28) In the thirty and first year of Asa . . . began Omri to reign--The twelve years of his reign are computed from the beginning of his reign, which was in the twenty-seventh year of Asa's reign.