This first post will simply lay out the more prominent Scriptural citations supporting the moral legitimacy of capital punishment, either explicitly or by inference. I won't attempt to argue Old vs. New Testament issues, as I generally deny the false dichotomy some posit between the moral law of the Old Covenant and that of the New. They are the same, even while many ritual requirements ("the Law") were indeed abrogated by the New Covenant. But moral teachings are always constant and unchanging, coming as they do from one and the same Lawgiver. Their applicability may change (e.g., we do not have to execute adulterers and other sexual sinners); but the principle of whether the state may justly execute offenders does not change. Here is a good summary of my views on these issues.
Here then is a quick look at Scriptural sources supporting the morality of the death penalty:
"Whoever kills any man shall surely be put to death.... You shall have the same law for the [foreigner] and for one from your own country; for I am the Lord your God."--Lev. 24:17-22
"Defile not the land of your habitation, which is stained with the blood of the innocent: neither can it otherwise be expiated, but by his blood that hath shed the blood of another."--Num. 35:33
"He that curseth his father, or mother, dying let him die: he hath cursed his father, and mother, let his blood be upon him. If any man commit adultery with the wife of another, and defile his neighbour's wife, let them be put to death, both the adulterer and the adulteress. If a man lie with his stepmother, and discover the nakedness of his father, let them both be put to death: their blood be upon them. If any man lie with his daughter in law, let both die, because they have done a heinous crime: their blood be upon them. If any one lie with a man as with a woman, both have committed an abomination, let them be put to death: their blood be upon them. If any man after marrying the daughter, marry her mother, he hath done a heinous crime: he shall be burnt alive with them: neither shall so great an abomination remain in the midst of you. He that shall copulate with any beast or cattle, dying let him die, the beast also ye shall kill. The woman that shall lie under any beast, shall be killed together with the same: their blood be upon them. If any man take his sister, the daughter of his father, or the daughter of his mother, and see her nakedness, and she behold her brother's shame: they have committed a crime: they shall be slain, in the sight of their people, because they have discovered one another's nakedness, and they shall bear their iniquity. If any man lie with a woman in her flowers, and uncover her nakedness, and she open the fountain of her blood, both shall be destroyed out of the midst of their people. Thou shalt not uncover the nakedness of thy aunt by thy mother, and of thy aunt by thy father: he that doth this, hath uncovered the shame of his own flesh, both shall bear their iniquity."--Leviticus, 20: 9-20
"If any man strike with iron, and he die that was struck: he shall be guilty of murder, and he himself shall die. If he throw a stone, and he that is struck die: he shall be punished in the same manner. If he that is struck with wood die: he shall be revenged by the blood of him that struck him. The kinsman of him that was slain, shall kill the murderer: as soon as he apprehendeth him, he shall kill him. If through hatred any one push a man, or fling any thing at him with ill design: Or being his enemy, strike; him with his hand, and he die: the striker shall be guilty of murder: the kinsman of him that was slain as soon as he findeth him, shall kill him."--Numbers 35: 16-21.
Therefore he that resisteth the power, resisteth the ordinance of God, and they that resist purchase to themselves eternal damnation. For rulers are not a terror to the good work, but to the evil. . . For he is the minister of God to thee for good. But if thou do that which is evil, fear: for he beareth not the sword in vain. For he is the minister of God: and avenger to execute wrath upon him that doth evil.--Rom. 13:2-4.