When we talk about justifiable killing we must always remember to use discernment. Just because you can kill someone doesn’t mean you should.
We are no longer under the Old Testament law so we are not to kill people for things like adultery, being a rebellious child, or homosexuality.
We are to always obey the law. Besides the Old Testament reasons here are four more reasons when killing is permitted.
Exodus 22:2–3 If a thief is found breaking in and is struck so that he dies, there shall be no bloodguilt for him, but if the sun has risen on him, there shall be bloodguilt for him. He shall surely pay. If he has nothing, then he shall be sold for his theft.
Luke 22:35-39 Then Jesus asked them, “When I sent you without purse, bag or sandals, did you lack anything?” “Nothing,” they answered. He said to them, “But now if you have a purse, take it, and also a bag; and if you don’t have a sword, sell your cloak and buy one. It is written: ‘And he was numbered with the transgressors ; and I tell you that this must be fulfilled in me. Yes, what is written about me is reaching its fulfillment.” The disciples said, “See, Lord, here are two swords.” “That’s enough!” he replied. Jesus went out as usual to the Mount of Olives, and his disciples followed him.
2. Protect your family
1 Timothy 5:8 But if anyone does not provide for his relatives, and especially for members of his household, he has denied the faith and is worse than an unbeliever.
Ephesians 5:25 Husbands, love your wives, just as Christ loved the church and gave himself up for her.
Ecclesiastes 3:8 A time to love, and a time to hate; a time of war, and a time of peace.
Joshua 4:13 About 40,000 ready for war passed over before the Lord for battle, to the plains of Jericho.
Ecclesiastes 3:8 a time to love, and a time to hate; a time for war, and a time for peace.
Psalm 18:34 He trains my hands for battle; he strengthens my arm to draw a bronze bow.
4. The death penalty for a serious crime.
Leviticus 24:17 Anyone who takes another person’s life must be put to death.
Romans 13:1-5 Let everyone be subject to the governing authorities, for there is no authority except that which God has established. The authorities that exist have been established by God. Consequently, whoever rebels against the authority is rebelling against what God has instituted, and those who do so will bring judgment on themselves. For rulers hold no terror for those who do right, but for those who do wrong. Do you want to be free from fear of the one in authority? Then do what is right and you will be commended. For the one in authority is God’s servant for your good. But if you do wrong, be afraid, for rulers do not bear the sword for no reason. They are God’s servants, agents of wrath to bring punishment on the wrongdoer. Therefore, it is necessary to submit to the authorities, not only because of possible punishment but also as a matter of conscience.
5. Old Testament reasons
Deuteronomy 21:18-21 If someone has a stubborn and rebellious son who does not obey his father and mother and will not listen to them when they discipline him, his father and mother shall take hold of him and bring him to the elders at the gate of his town. They shall say to the elders, “This son of ours is stubborn and rebellious. He will not obey us. He is a glutton and a drunkard.” Then all the men of his town are to stone him to death. You must purge the evil from among you. All Israel will hear of it and be afraid.
Leviticus 20:27 “A man or a woman who is a medium or a necromancer shall surely be put to death. They shall be stoned with stones; their blood shall be upon them.”
Exodus 31:15 For six days work is to be done, but the seventh day is a day of sabbath rest, holy to the LORD. Whoever does any work on the Sabbath day is to be put to death.
Leviticus 20:10 If a man commits adultery with his neighbor’s wife, both the man and the woman who have committed adultery must be put to death.
Leviticus 20:13 If a man practices homosexuality, having sex with another man as with a woman, both men have committed a detestable act. They must both be put to death, for they are guilty of a capital offense.