Why did God kill people in the Old Testament (OT)?
◄ Christian Response STRONG The primary reason was punishment for wrongdoing.
The populations of the destroyed cities had long histories of grievous sins (Gen 15:16, Dt 25:17-19), which often included sacrificing their children to false gods (Dt 12:29-31). Their consciences should have told these people they were doing wrong. Had they listened and changed their ways, they would not have been destroyed. God has said that if any nation is about to be destroyed as punishment but repents, he will forgive them and not destroy them (Jer 18:7-8). In fact, this occurred in the city of Ninevah (Jonah 3:4-10).
http://www.rationalchristianity.net/genocide.html
◄ Christian Response STRONG To avoid corrupting Israel into doing the same sins.
In the cities that were given to the Israelites as their inheritance, there was a secondary reason: totally depraved cultures were destroyed so that they would not corrupt the Israelites into committing the same evil acts (Dt 7:1-4, 20:16-18). This did in fact occur: when the Israelites didn’t obey God and destroy cities, they too began practicing child sacrifice (Ps 106:34-40).
http://www.rationalchristianity.net/genocide.html
◄ Christian Response STRONG It served as a warning.
The destruction of wicked nations served as an instructive warning to contemporaries (Josh 2:1-11) and future generations (1 Cor 10:1-11).
http://www.rationalchristianity.net/genocide.html