Jamieson, Fausset and Brown on Numbers 22:19-20

19-20. tarry ye also here this night, that I may know what the Lord will say unto me more--The divine will, as formerly declared, not being according to his desires, he hoped by a second request to bend it, as he had already bent his own conscience, to his ruling passions of pride and covetousness. The permission granted to Balaam is in accordance with the ordinary procedure of Providence. God often gives up men to follow the impulse of their own lusts; but there is no approval in thus leaving them to act at the prompting of their own wicked hearts (Jos 13:27).