“this Jordan.” Israel was camped just east of the Jordan River. The Israelites had already heard about the Jordan River when God described the boundaries of the land.
“cross over this Jordan, you and all the people, to the land that I am giving to them.” In a very real sense, the book of Joshua is a fulfillment of the promises of God to give Israel the land (cp. Josh. 1:6; 21:45). The book of Joshua is typological of Jesus and his work in many ways. One of them is that, although God made available the Promised Land, the people had to cross over the Jordan to get it. Similarly, God has made salvation through Christ and the future Promised Land available, but people must act to receive it.
Crossing over the Jordan and inheriting the Promised Land is a major theme in Joshua.