Joshua reveals that God hates sin because He loves people. (This is the message statement.) Of course He also hates sin because it offends His holiness. However in Joshua I believe the emphasis is on God's concern for the Israelites more than the vindication of His holiness.
The writer of this book portrayed Yahweh as a God of war. This side of God's character has created problems for many people. How could God be loving and yet deal so severely with the Canaanites? In view of Jesus Christ's commands to love our enemies (Matt. 5:44) and be peacemakers (Matt. 5:9) how can we justify God's dealings with the Canaanites that this book records?
The righteous side of God's character is, of course, a consistent emphasis throughout Scripture. In the Pentateuch God dealt severely with all those who oppressed the patriarchs and their descendents (cf. Exod. 15:3). In the historical books we find the same thing. The psalmist referred to Yahweh as "mighty in battle"against the forces opposed to His will (e.g., Ps. 24:8; 45:3). The prophets, especially Jeremiah, warned that God will judge sin. In the Gospels we hear and see the wrath of God manifested in Jesus' words and works against the Pharisees for their sins. In the Book of Revelation, especially chapters 6-19, John pictured the wrath of God being poured out in judgment on the whole world. In Joshua, too, we see God commanding and leading the Israelites in violent mortal conflict with sinners.
The reason God wages war against sin and sinners is that He loves people and wants to save them from destruction by sin and its consequences (cf. Rom. 6:23). If God is not a God of war, then He cannot be a God of love.
We can see God's hatred of sin in His dealings with the Canaanites and in His dealings with the Israelites in Joshua.
In the Pentateuch we discovered many statements and warnings about the Canaanites. Their wickedness was great even in Abraham's day. The Sodomites were Canaanites (Gen. 19), but the measure of their iniquity was not yet full (Gen. 15:16; cf. Lev. 18:24-28). The Ras Shamra Tablets have shed much light on Canaanite religion and culture. Archaeologists discovered these written records in northwest Syria at the site of an ancient city, Ugarit. They date from the fourteenth century B.C., the time of the conquest by Joshua.
The Canaanites wrote them in the Ugaritic language in cuneiform script. These records reveal that Canaanite culture was extremely immoral and inhumane. The Canaanites practiced prostitution of both sexes, many kinds of sexual perversion, and human sacrifice widely. They were religious practices.
As Israel anticipated entering the land occupied by these people it was a case of destroy or be destroyed. In commanding the Israelites to annihilate the Canaanites God was performing surgery to remove a cancer from human society. He was not murdering an innocent primitive people as the liberal critics of the Bible used to say. God had been extremely patient with the Canaanite tribes. They had had hundreds of years to repent after the witness of Melchizedek, Abraham, and many other God-fearing people who had lived among them. Because they did not repent, God used Israel as a broom to sweep away their filth and purify the land. He did not drive the Canaanites out simply to make room for Israel. He did so also to remove this cancerous society and its malignant influence. Israel exercised considerable restraint in dealing with the Canaanites compared with the way some other ancient Near Eastern countries dealt with people they defeated. The Assyrians, for example, were very brutal.
God also manifested His hatred of sin in His dealings with the Israelites. We have seen this already in the Pentateuch as God disciplined His chosen people when they sinned. In Joshua, when Israel lusted after the things of Canaan He dealt with her severely. Achan's sin (ch. 7) affected the whole nation. God judged Achan as He did to teach the Israelites a strong lesson concerning how serious sin is. God's dealings with His own people were even more severe than His dealings with the Canaanites.
In short, Joshua reveals that God wages war against sin wherever He finds it. He patiently waits for people to repent, but if they do not judge sin themselves, He will judge it (Acts 17:30-31; 1 Cor. 11:31). God deals more severely with His own people than with others because privilege heightens responsibility.
Not only does Joshua reveal that God wages war against sin, but it also teaches us how He does it.
God uses the forces of nature to wage war against sin. He restrained the waters of a river, shook the walls of a city, sent hail from heaven, and lengthened the hours in a day to accomplish His purposes. God rarely works in as direct ways to judge sin today. This should not lead us to conclude that He never did or never will. He will again shake the heavens and the earth to bring down His wrath on sinners (cf. Rev. 6-19). We have the privilege of living in the day of His grace when God is being patient with sinners (2 Pet. 3:9-10). Nevertheless that day will end, and He will bring judgment on our world as He did on the world of the Canaanites.
God also uses people who are loyal to Him to wage war against sin. The people God used in Joshua were men and women of faith (Heb. 11:30). God's methods are unpredictable and often seem strange to His servants. They frequently appear foolish to us. Therefore God asks that we simply trust and obey Him. Faith in Joshua means refraining from what God forbids (e.g., at Ai) as well as doing all that God directs (e.g., at Jericho). Joshua is one of the clearest illustrations in the Bible that consistent trust in and obedience to the Word of God results in overcoming, victorious, powerful, successful living. Joshua clarifies three characteristics of faith.
1. Faith involves accepting God's standard of holiness. We tend to undervalue the need for personal and corporate holiness in our day because God is not judging sin immediately as He did in Joshua's day. This is the day of His patience. Nevertheless Joshua teaches that without holiness there can be no spiritual power or consistent victory in our experience (cf. 1:8; 24:19-25).
2. Faith also means abandonment to God's will. God has revealed in His Word how His people can experience all He wants them to have. Because God's ways are not the ways we would choose from our finite carnal viewpoint we have trouble trusting God and committing ourselves wholeheartedly to His will. The Israelites succeeded at Jericho as they did because they committed themselves completely to engaging in that battle as God had commanded. They did so even though it must have looked like suicide to obey.
3. Faith also involves achievement in God's might. It is God who wins the victories. Without God His people can do nothing productive (John 15:5). However with Him all things are possible (Matt. 19:26; Phil. 4:13). The Israelites learned this when they failed at Ai. Success does not really come as a result of our action as we obey God. It comes as a result of God's action working through instruments that He finds usable.
In summary, Joshua reveals that God hates sin. He is at war with it because it offends Him but also because it destroys the people He has created to have fellowship with Himself. God uses the forces of nature and people who are loyal to Him to root out sin and bring deliverance to His people. However the people He uses must accept His standard of holiness for themselves. They must abandon themselves to His way of doing things. They must also acknowledge that victories are the result of His might, not their own.
