John Gill Commentary 2 Chronicles 19:4

"And Jehoshaphat dwelt at Jerusalem: and he went out again among the people from Beer-sheba to the hill-country of Ephraim, and brought them back unto Jehovah, the God of their fathers." — 2 Chronicles 19:4 (ASV)

And Jehoshaphat dwelt at Jerusalem
And went out no more to Samaria, nor concerned himself about the affairs of Israel, but attended to his own:

and he went out again through the people ;
took a tour throughout his dominions now, in his own person, as before by his princes, with the priests and Levites:

from Beersheba to Mount Ephraim ;
Beersheba was the southern boundary of the land of Judah, and Mount Ephraim lay to the north, and was the northern boundary of it since the division of the kingdom:

and brought them back to the Lord God of their fathers ;
from idolatry to the pure worship of God, such who had relapsed since the first reformation, or had not been influenced by it.