David Killed People

God did not design us for violence. Sin, however, changed everything and it became the responsibility of righteous people to take violent situations in hand. 

As soon as Noah stepped off of the ark God instructed him that any man or beast who took the life of another man was to be put to death, Genesis 9:5-6. God had noted for us in Genesis 6:5 & 11 & 13 that mankind had become steeped in violence. God’s plan was that the criminally violent were to be met with judicial violence.

Abram had 318 servants who were apparently trained for war. He used them to rescue the citizens of Sodom and Gomorrah and to destroy those who had taken them captive, Genesis 14:1-4. For this, Abram was blessed by Melchizedek, God’s priest who was also a type for the Christ. Melchizedek attributed Abram’s success in battle to God.
 
Many other of God’s leaders “took up the sword” so to speak in defense of justice and the oppressed. Moses killed an Egyptian for abusing a Hebrew. Joshua lead Israel in conquering Canaan. Samson killed thousands of spiritually rebellious Philistines in service to God. Check Judges 14:4 specifically on this.
 
Jesus is the one who teaches us to love one another sacrificially. He is also the one who teaches us that when He returns He will cast the wicked into a lake of fire with the devil and his angels, Matthew 25:41. Jesus died to provide salvation for us, but those who refuse will suffer eternal death. Our Lord believes in capital punishment.
 
David, a man after God’s own heart (Acts 13:22) killed Goliath and untold others as God’s leader of Israel. He wrote of his warrior spirit, “Blessed be the Lord my rock, who trains my hands for war, and my fingers for battle”, Psalm 144:1
 
Until Jesus’ return, God has placed the responsibility for the punishment of evil in the hands of world governments according to Romans 13:1-5. They do not bear the sword in vain. Those who serve in the military or on police forces therefore, are God’s sword for peace.