Yahweh said to Joshua, This day will I begin to magnify you in the sight of all Israel, that they may know that, as I was with Moses, so I will be with you.
Evidently the pushing back of the waters of the Jordan was to be a sign to the Israelites that God would push back the Canaanites (Joshua 3:10). The title "the Lord of all the earth" occurs here (Joshua 3:11) first in Scripture indicating Yahweh’s absolute sovereignty over this planet. Because He was "the Lord of all the earth" He could give Canaan to the Israelites.