Some translations use the word “kill,” but the word is better translated “murder” in this passage. Murder is the unlawful, intentional taking of a life with malice.
Right after this command was given, God instructed the Levites to take up the sword and kill people who had turned to idolatry. God was not being contradictory under the law He had just given to Moses, for the killing was administered justice.
While the Bible places great value on human life, this specific command is not the foundation of New Testament, biblical nonresistance.