1-kings 16:23

In the thirty and first year of Asa - There must be a mistake here in the number thirty-one; for, in 1 Kings 16:10 and 1 Kings 16:15, it is said that Zimri slew his master, and began to reign in the twenty-seventh year of Asa; and as Zimri reigned only seven days, and Omri immediately succeeded him, this could not be in the thirty-first, but in the twenty-seventh year of Asa, as related above. Rab. Sol. Jarchi reconciles the two places thus: "The division of the kingdom between Tibni and Omri began in the twenty-seventh year of Asa; this division lasted five years, during which Omri had but a share of the kingdom. Tibni dying, Omri came into the possession of the whole kingdom, which he held seven years; this was in the thirty-first year of Asa. Seven years he reigned alone; five years he reigned over part of Israel; twelve years in the whole. The two dates, the twenty-seventh and thirty-first of Asa, answering, the first to the beginning of the division, the second to the sole reign of Omri." Jarchi quotes Sedar Olam for this solution.

16:23 Twelve years — That is, and he reigned twelve years, not from this thirty-first year of Asa, for he died in his thirty-eighth year, verse 29, but from the beginning of his reign, which was in Asa's twenty-seventh year, verse 15,16. So he reigned four years in a state of war with Tibni, and eight years peaceably.