Below are Bible verses that speak about the killing of non-believers or idolaters, mostly from the Old Testament, where such actions were often commanded in specific historical contexts.

Old Testament Verses

If your brother, the son of your mother, your son or your daughter, the wife of your bosom, or your friend who is as your own soul, secretly entices you, saying, ‘Let us go and serve other gods,’ … you shall surely kill him; your hand shall be first against him to put him to death, and afterward the hand of all the people.
And you shall stone him with stones until he dies…
~ Deuteronomy 13:6–10, NKJV

If there is found among you … a man or a woman who has been wicked in the sight of the Lord your God, in transgressing His covenant, who has gone and served other gods and worshiped them … then you shall bring out to your gates that man or woman … and stone to death that man or woman with stones.
~ Deuteronomy 17:2–5, NKJV

He who sacrifices to any god, except to the Lord only, he shall be utterly destroyed.
~ Exodus 22:20, NKJV

Thus says the Lord of hosts: ‘I will punish Amalek … Now go and attack Amalek, and utterly destroy all that they have, and do not spare them. But kill both man and woman, infant and nursing child, ox and sheep, camel and donkey.’
~ 1 Samuel 15:2–3, NKJV

A divine command for total war against the Amalekites — often interpreted by scholars as a unique act of divine judgment, not a general law. Now therefore, kill every male among the little ones, and kill every woman who has known a man intimately. But keep alive for yourselves all the young girls who have not known a man intimately.
~ Numbers 31:17–18, NKJV

New Testament: No Commands to Kill Non-Believers

There are no verses in the New Testament commanding believers to kill non-believers. In fact, the teachings of Jesus emphasize the opposite:

But I say to you, love your enemies, bless those who curse you, do good to those who hate you, and pray for those who spitefully use you and persecute you.
~ Matthew 5:44, NKJV

Jesus answered, ‘My kingdom is not of this world. If My kingdom were of this world, My servants would fight… but now My kingdom is not from here.’
~ John 18:36, NKJV

If anyone comes to you and does not bring this doctrine, do not receive him into your house nor greet him; for he who greets him shares in his evil deeds.
~ 2 John 1:10–11, NKJV

Note on Interpretation
These Old Testament verses are generally understood by Christian scholars as historical commands to ancient Israel under specific circumstances. They are not applied to modern Christians as general instructions. The New Testament brought a shift from national law to spiritual and moral guidance.