After three days the officers went through the camp
2. And it came to pass after three days, etc That is, three days after their departure had been intimated. For they did not halt at the bank longer than one night. But as the period of three days had previously been fixed for crossing, and they had no hope of being able to accomplish it, Joshua now exhorts them to pay no more regard...
Rahab, in mentioning to the spies the drying up of the Red Sea (Jos 2:10), the report of which terrified the Canaanites more than anything else, intimates that those on that side the water expected that Jordan, that great defence of their country, would in like manner give way to them. Whether the Israelites had any expectation of it does not appear.
Commenting on Joshua 3:1-6
And it came to pass after three days,.... At the end of the three days they were bid to prepare food for their expedition, and to go over Jordan, Jos 1:11, that the officers went through the host; the camp of Israel; very probably the same as in Jos 1:10; this was, no doubt, by the order of Joshua, and who was directed to it by the Lord.