'Killing' in the Bible

because all [the] firstborn [are] mine; on the day of my killing all [the] firstborn in the land of Egypt, I consecrated for myself all [the] firstborn in Israel, {both humankind and animal}; they will be mine. I am Yahweh."

The Lord said to Moses, “Take all the leaders of the people [who have committed sin with the Moabites], and execute them in broad daylight before the Lord, so that the fierce anger of the Lord may turn away from Israel.”

They fought against the Midianites just as the LORD had commanded Moses, killing every man.

You are not to accept a ransom for the life of a murderer who is guilty of killing someone; he must be put to death.