1 Kings 15 New International Version (NIV) Abijah King of Judah 15 In the eighteenth year of the reign of Jeroboam son of Nebat, Abijah became king of Judah, 2 and he reigned in Jerusalem three years. His mother’s name was Maakah daughter of Abishalom. 3 He committed all the sins his father had done before him; his heart was not fully devoted to the Lord his God, as the heart of David his forefather had been. 4 Nevertheless, for David’s sake the Lord his God gave him a lamp in Jerusalem by raising up a son to succeed him and by making Jerusalem strong. 5 For David had done what was right in the eyes of the Lord and had not failed to keep any of the Lord’s commands all the days of his life—except in the case of Uriah the Hittite.
1 Kings 15:4
ESV - 4 Nevertheless, for David's sake the Lord his God gave him a lamp in Jerusalem, setting up his son after him, and establishing Jerusalem.
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The lamp is the tribe of Benjamin that God gave Rehoboam in 1 Kings 11:36. So most likely someone from the tribe of Benjamin was helping. It could be his wife was from the tribe of Benjamin.