John Gill Commentary Numbers 33:56

"And it shall come to pass, that, as I thought to do unto them, so will I do unto you." — Numbers 33:56 (ASV)

Moreover, it shall come to pass
This being the case, they suffering the Canaanites to dwell among them, and they mingling with them, learning their works, and serving their gods: that

I shall do unto you as I thought I should do unto them ;
deliver them up into the hands of their enemies, who should carry them captive into other lands.