I get it directly from the bible.
Anyone arrogant enough to reject the verdict of the judge or of the priest who represents the LORD your God must be put to death. Such evil must be purged from Israel. (Deuteronomy 17:12 NLT)
You should not let a sorceress live. (Exodus 22:17 NAB)
A man or a woman who acts as a medium or fortuneteller shall be put to death by stoning; they have no one but themselves to blame for their death. (Leviticus 20:27 NAB)
Whoever strikes his father or mother shall be put to death. (Exodus 21:15 NAB)
If one curses his father or mother, his lamp will go out at the coming of darkness. (Proverbs 20:20 NAB)
All who curse their father or mother must be put to death. They are guilty of a capital offense. (Leviticus 20:9 NLT)
If a man commits adultery with another man's wife, both the man and the woman must be put to death. (Leviticus 20:10 NLT)
Whoever sacrifices to any god, except the Lord alone, shall be doomed. (Exodus 22:19 NAB)
They entered into a covenant to seek the Lord, the God of their fathers, with all their heart and soul; and everyone who would not seek the Lord, the God of Israel, was to be put to death, whether small or great, whether man or woman. (2 Chronicles 15:12-13 NAB)
And my all time favorites...
If your own full brother, or your son or daughter, or your beloved wife, or you intimate friend, entices you secretly to serve other gods, whom you and your fathers have not known, gods of any other nations, near at hand or far away, from one end of the earth to the other: do not yield to him or listen to him, nor look with pity upon him, to spare or shield him, but kill him. Your hand shall be the first raised to slay him; the rest of the people shall join in with you. You shall stone him to death, because he sought to lead you astray from the Lord, your God, who brought you out of the land of Egypt, that place of slavery. And all Israel, hearing of this, shall fear and never do such evil as this in your midst. (Deuteronomy 13:7-12 NAB)
Suppose a man or woman among you, in one of your towns that the LORD your God is giving you, has done evil in the sight of the LORD your God and has violated the covenant by serving other gods or by worshiping the sun, the moon, or any of the forces of heaven, which I have strictly forbidden. When you hear about it, investigate the matter thoroughly. If it is true that this detestable thing has been done in Israel, then that man or woman must be taken to the gates of the town and stoned to death. (Deuteronomy 17:2-5 NLT)
Ahhh, I see you are most proficient at copying and pasting young grasshopper, but are you proficient at understanding?
There are indeed violent passages in the Old Testament. But Christians who use violence in the name of God have no justification for their actions from Jesus Christ, his life and teachings as found in the New Testament. Some Christians have indeed committed many horrible acts, but when they have done this, they have betrayed the very person that they claim to follow.
We find themes in the Old Testament of God is using Israel as an instrument of His justice to purge the land of its sinfulness. Later in history God used other nations like the Assyrians and the Babylonians as His instruments to cleanse the land by destroying the people of Israel for their sinfulness. Keep in mind those passages were for a specific people, a specific time and place, and a specific purpose. Nowhere in the later Old Testament period do we see God commanding the nation of Israel to go and attack as a way to promote faith in God.