John Gill Commentary Joshua 3:10

"And Joshua said, Hereby ye shall know that the living God is among you, and that he will without fail drive out from before you the Canaanite, and the Hittite, and the Hivite, and the Perizzite, and the Girgashite, and the Amorite, and the Jebusite." — Joshua 3:10 (ASV)

And Joshua said
To the people as follows:

hereby you shall know that the living God [is] among you ;
who has life in and of himself, and is the author of life to all his creatures; and is so called in opposition to the lifeless idols of the Gentiles: and it may be, as Abarbinel observes, to suggest to them, that though Moses was dead, the Lord lived, and lives for evermore; and by the following miracle of dividing the waters of Jordan, it would be a plain case that the Lord was yet among them, to protect and defend them, deliver and save them:

and [that] he will without fail drive out from before you the
Canaanites, and the Hittites, and the Hivites, and the Perizzites, and
the Girgashites, and the Amorites, and the Jebusites ;
all the seven nations are mentioned, even the Girgashites, who are sometimes omitted, to assure them of the expulsion of them all, to make way for their entire possession of the land of Canaan, as had been promised them.