Samuel 1:17

"David and Goliath confront each other, Goliath with his armor and shield, David with his staff and sling. "The Philistine cursed David by his gods," but David replies: "This day the LORD will deliver you into my hand, and I will strike you down, and cut off your head; and I will give the dead bodies of the host of the Philistines this day to the birds of the air and to the wild beasts of the earth; that all the earth may know that there is a God in Israel, and that all this assembly may know that God saves not with sword and spear; for the battle is God's, and he will give you into our hand."

Joshua 10:10

"And the LORD discomfited them before Israel, and slew them with a great slaughter at Gibeon, and chased them along the way that goeth up to Bethhoron, and smote them to Azekah, and unto Makkedah."

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here is one reply from a forum:

"When it is rightly understood, there are no contradictions in the Bible. There are, however, many seeming contradictions. You point out a good one. How can God issue a Commandment that states, "Thou shall not kill" (Ex. 20:13), and yet in the very next chapter say, "Whoever curses his father or mother shall be put to death" (Ex. 21:17)? The answer is that the Commandment is not to be understood as a blanket condemnation of taking life. The larger context makes that clear. For example, Moses, who received the Ten Commandments directly from God & spoke to God face to face, did not view all killing as a violation of the Commandment given in Ex. 20:13 & Deut. 5:17. He advised the Israelites, "But in the cities of those nations which the LORD, your God, is giving you as your heritage, you shall not leave a single soul alive" (Deut. 20:16).

The Commandment, when properly viewed in the light of the rest of the Bible, would be better translated as, "Thou shall not murder." The taking of life has never been prohibited in the Bible. What is prohibited is the taking of innocent life, that is, murder."