The strangers — i.e., the non-Judæans; members of the northern kingdom. A similar accession to the southern kingdom had taken place under Rehoboam (2 Chronicles 11:16); and another yet is related in the reign of Hezekiah (2 Chronicles 30:11; 2 Chronicles 30:18).
And out of Simeon. — This tribe is again mentioned along with Ephraim and Manasseh in 2 Chronicles 34:6, although its territory lay “within the inheritance of the children of Judah” (Joshua 19:1). Perhaps a portion of the tribe had migrated northward (comp. Judges 18), and some of these now settled again in Judah. Genesis 49:7 speaks of Simeon as “divided in Jacob, and scattered in Israel.”
Another solution is, that although politically one with Judah, the tribe of Simeon was religiously isolated by its illegal worship established at Beersheba, similar to that at Bethel and Dan (Amos 4:4; Amos 5:5; Amos 8:14). But this hardly agrees with the next clause: “They fell to him out of Israel.”
They fell to him. — (1 Chronicles 12:19; 2 Kings 7:4.)
When they saw that the Lord. — They had heard of his great deliverance from Zerah.
In the fifteenth year of the reign of Asa. — This seems to indicate that the Cushite invasion took place not long before, perhaps in the spring of the same year (see Note on 1 Chronicles 20:1).