The Book of Joshua marks a transition, as the Israelites entered and occupied Canaan. From Exodus to Deuteronomy, the people had travelled towards Canaan, fulfilling promises given in Genesis. The books from Judges to Esther describe the history of Israel's occupation in, and later removal from, Canaan.
The book covers a period of around 25 years.
v1-2: God's servant Moses was dead, but His work continued. He had prepared a new leader, Joshua, to whom He spoke. God had clearly chosen Joshua as leader, and the people had come to respect him too, Deut 34.9. Joshua had experience, and had served with Moses for many years. The first reference is leading the army against the Amalekites in Ex 17.8-9.
To Joshua was assigned the specific task of leading the people into the land, and encouraging obedience to God's ways.
v3-6: God gave promises to Joshua as an individual, and to the people.
God was going to give them the land (v2); the land belonged to Israel, their task was to occupy it. As they walked in it, they would occupy it (v3). The area of land was large (v4).
God gave authority to Joshua, and a promise of His protection. God had given Him a work to do, and he could not die before that was completed. God also promised His presence; He would remain with Joshua, just as He had with Moses. Joshua had therefore to be courageous, to obey God's call, and to lead the people into the land. Even here is a sense of personal relationship with God, beyond a cold obedience to the commands of the law.
v7-9: The law was very important; Joshua could not risk departing from it, for in it were the promises of personal and national blessing. In the law, God's purposes were revealed for all His people, and for each of His people. We cannot truly enjoy the "do not fear, I am with you" without knowledge of the word of God that pronounces those blessings.
God's law to be in his "mouth", compare Mal 2.6, for Joshua was to speak words of truth. He was also to meditate on it, so that his mind was full of God's truth. The result was obedience, "to do everything"; for Joshua could not put aside any part of what God had said. Joshua would also find courage (v9) in obedience; he could do what naturally he could not do. Again, God gave the promise of His presence.
We note no reference to the enemies of Israel here; God's promises would be fulfilled anyway, and obedience is always the proper route to follow.
The Lord Jesus Christ commanded His apostles to teach His followers to "obey everything I have commanded" (Matt 28.20); thus, the words addressed here to Joshua are reflected in the N.T. We should meditate on God's word, speak of it, and obey it.
v11: Joshua repeated the earlier promises of entering the land; he now commanded the people to get ready.
v12: Joshua addressed the tribes of Reuben and Gad, and the half-tribe of Manasseh, who had chosen land east of the Jordan.
v13: Many times, God had promised the land, to Abraham (Gen 12.1; 13.14-15; 15.18-21; 17.8), to Jacob (Gen 28.13-14; 48.21), to Joseph (Gen 50.24), and to Moses (Ex 3.8,17; 6.8; 13.5,11; 23.31; Num 13.1; Deut 6.23; 34.4); it would be that, through Joshua, centuries of prophesies would be fulfilled. But those tribes had effectively chosen something else, something less than God's best.
The land of Canaan was a place of rest (Lev 26.6; Deut 6.10-11); a place of bounty (Ex 3.8; Lev 26.5; Deut 11.10-12; 33.28); and a place of triumph (Deut 7.1). It was also a place of conflict, since Israel could only gave her inheritance through warfare.
v14-15: Moses had given the land east of the Jordan to the two and a half tribes; Joshua honoured this, but did insist that those tribes honour their word to help their brothers occupy the land west of the Jordan.
v16-18: The two and a half tribes promised Joshua that they would support him. They claimed to have obeyed Moses in all things, which they clearly had not, otherwise they would not have settled east of Jordan. Even so, they declared allegiance to Joshua.