At that time - The phrase here connects the narrative which follows with Jeroboam’s persistence in his evil courses. The event related is the first judgment upon him for his obduracy, the beginning of the cutting off of his house from the face of the earth.
Abijah - We see by this name that Jeroboam did not intend to desert the worship of Yahweh, since its signification is “Yahweh is my father,” or “Yahweh is my desire” Job 34:36.