‘ Then Joshua commanded the officers of the people, saying “Pass through the midst of the camp and command the people, saying, ‘Prepare victuals, for in three days you are to pass over this Jordan, to go in to possess the land which YHWH your God gives you to possess it.' ” '
The officers (shoterim) of the people are mentioned in Deuteronomy 1:15; Deuteronomy 20:5-9. They were the chief men of the tribes. In Deuteronomy 16:18 they are parallel with the judges. Moved by his dream Joshua told them to prepare the people for the crossing of the River. Although they were still receiving the manna (Joshua 5:12), that would not be so easily gatherable on a war footing, and anyway it would shortly cease, so they needed to ensure that they were well provisioned. Now that they were out of the wilderness and close to the land, plenty of food would be available, such for example as they had captured in battles against the Amorites. The word for ‘victuals' also includes hunted game.
“In three days.” That is, in a short time. ‘Three days' is a standard way of saying ‘a few days, shortly'. (It means any period less than the next step up, ‘seven days'). Time was not as precise for them as it is for us. Life was more relaxed.
“You are to pass over this Jordan, to go in to possess the land which YHWH your God gives you to possess it.” Compare Deuteronomy 11:31; Deuteronomy 1:8; Deuteronomy 3:18. Moses' words were burned into Joshua's mind and became God's voice to him. Notice his encouragement to the people, they were to possess what God had given them to possess. Thus they could be sure that He would enable them.