2 Chronicles 11:13

And the priests and the Levites that were in all Israel resorted to him out of all their coasts.

The priests and the Levites throughout all Israel left their own districts and homes and came to Rehoboam at Jerusalem, joining his kingdom. They fled the northern kingdom because Jeroboam's new worship and priesthood did not meet God's requirements, and they desired to worship faithfully. Their coming was part of a wider movement of God-fearing Israelites from the northern tribes who set their hearts to seek the Lord so that they could worship Him faithfully at Jerusalem. This influx of faithful people strengthened Judah and Rehoboam during the three years in which they walked in the way of David and Solomon.