(1) Abijam.--The form of the name given in 2 Chronicles 13, "Abijah," is probably correct, as having a more distinct significance. The variation here, if not (as some think) a mere false reading, may have been made for the sake of distinction from the son of Jeroboam.

Pulpit Commentary

Verse 1. - Now in the eighteenth year of king Jeroboam, the son of Nebat, reigned Abijam [see note on 1 Kings 14:31. It is implied in 2 Chronicles 11:20-22 that he was not the firstborn among Rehoboam's twenty-eight sons, but the eldest son of the favourite wife. As he left behind him thirty-eight children (2 Chronicles 13:21) at his decease, some three years later, he must have been of considerable age at his accession. This consideration rather favours the idea that Rehoboam was "forty and one years old when he began to reign" (2 Chronicles 12:13)] over Judah.

Matthew Henry's Concise Commentary

15:1-8 Abijam's heart was not perfect with the Lord his God; he wanted sincerity; he began well, but he fell off, and walked in all the sins of his father, following his bad example, though he had seen the bad consequences of it. David's family was continued as a lamp in Jerusalem, to maintain the true worship of God there, when the light of Divine truth was extinguished in all other places. The Lord has still taken care of his cause, while those who ought to have been serviceable thereto have lived and perished in their sins. The Son of David will still continue a light to his church, to establish it in truth and righteousness to the end of time. There are two kinds of fulfilling the law, one legal, the other by the gospel. Legal is, when men do all things required in the law, and that by themselves. None ever thus fulfilled the law but Christ, and Adam before his fall. The gospel manner of fulfilling the law is, to believe in Christ who fulfilled the law for us, and to endeavour in the whole man to obey God in all his precepts. And this is accepted of God, as to all those that are in Christ. Thus David and others are said to fulfil the law.

Gill's Exposition of the Entire Bible

Now in the eighteenth year of King Jeroboam the son of Nebat reigned Abijam over Judah. That is, began to reign; and by this it appears that Rehoboam was in the eighteenth year of his reign when he died, for he and Jeroboam began their reign at the same time.

BibleApps.com