John Gill Commentary Numbers 35:10

"Speak unto the children of Israel, and say unto them, When ye pass over the Jordan into the land of Canaan," — Numbers 35:10 (ASV)

Speak to the children of Israel, and say to them
Now, directly:

when you come over Jordan into the land of Canaan ;
as they quickly would, being now very near it, and of which there was the utmost certainty, since the Lord had promised to bring them over that river, and put them in possession of that land.