John Gill Commentary 2 Chronicles 20:29

"And the fear of God was on all the kingdoms of the countries, when they heard that Jehovah fought against the enemies of Israel." — 2 Chronicles 20:29 (ASV)

And the fear of God was on all the kingdoms of these
countries
Whose armies were slain, and all other neighbouring ones; for the word these is supplied:

when they had heard that the Lord fought against the enemies of Israel ;
and they were afraid to invade their land, or make war with them; nor did the Edomites dare to revolt in the times of Jehoshaphat.