2 Chronicles 15:9

And he gathered all Judah and Benjamin, and the strangers with
them
The proselytes of the gate:

out of Ephraim and Manasseh, and out of Simeon:
out of all the places in those tribes that had come off to him, or had been taken by him; for otherwise these belonged to the ten tribes under the government of Jeroboam, and his successors, and the next clause explains it:

for they fell to him out of Israel abundance, when they saw that the
Lord his God was with him;
as was clear by the victory he gave him over the Ethiopians; after that time many in the above tribes came over to him; the Targum is,

``when they saw the Word of the Lord his God was his help.''