John Gill Commentary 2 Chronicles 33:13

"And he prayed unto him; and he was entreated of him, and heard his supplication, and brought him again to Jerusalem into his kingdom. Then Manasseh knew that Jehovah he was God." — 2 Chronicles 33:13 (ASV)

And prayed unto him

To have mercy on him, and forgive him his sins.

and he was entreated of him, and heard his supplication ;

and granted his request, showed favour to him, and forgave him his sins:

and brought him again to Jerusalem into his kingdom ;

so wrought upon the heart of the king of Assyria, as to give him his liberty, and restore him to his dominions; it is very probable his captivity was not long; for, being soon brought by his affliction to a sense and confession of his sins, by the overruling providence of God, he was quickly released:

then Manasseh knew that the Lord he was God ;

and not the idols he had served; that he was a holy God, and hated sin, and a just God in afflicting him for it, and gracious and merciful in forgiving his sins, and bringing him out of his troubles.