In Numbers twenty-one, verse three, God, through Israel, destroyed the Caananites in the Negev. The destruction was a just act upon those who committed sin, immorality, violence, and unrighteousness. As the Lord of history, God has the right to decide when it is best to destroy the wicked to accomplish His redemptive purpose for the human race. In the Old Testament, God often used Israel to succeed for His people.
Under the new covenant, He no longer uses believers to destroy. At the end of the age, God will render judgment upon all who reject Christ and His way of salvation. The unbelievers do not understand what authority they are following. Whether they realize it or not, it is a force they cannot see in the flesh. If a person does not serve God, they are serving the world, which is, in reality, serving the devil.
God utterly destroys the Canaanites because their sin opposes God’s sinless being. He is light, and there is no darkness in Him at all. In the Israelites’ prayers and vows with acceptance heard, and answered them according to their wish: into their hands, gave them victory over them. The destruction is not the first time God had to eliminate a sinful group of people from the face of the earth.
The other incident where God utterly destroys man is in Genesis chapter six verse seven, where He said, “I will destroy man from off the face of the earth.” The earth was already showing signs of corruption when sons of God were taking wives of who they chose. God also saw the wickedness in the heart of man, which made Him feel sorry that He made man. The lust and violence were enough for God: utterly destroy them.
Today, there is still lust and violence in society. However, God will judge every man accordingly, whether good or bad.