The following is an excerpt from The MacArthur New Testament Commentary on Romans 13:4.

for it is a minister of God to you for good. But if you do what is evil, be afraid; for it does not bear the sword for nothing; for it is a minister of God, an avenger who brings wrath upon the one who practices evil. (13:4)

It is not wrong for Christians to look to their governments for protection of life and property. Paul took advantage of the government’s role in promoting what is good when he used his Roman citizenship to secure justice by appealing to Caesar (Acts 25:11). The apostle also experienced the protection of Roman law while he was in Ephesus on his third missionary journey. When a multitude was incited against him by Demetrius the silversmith, the town clerk took Paul into protective custody and warned the crowd against rioting, saying, “So then, if Demetrius and the craftsmen who are with him have a complaint against any man, the courts are in session and proconsuls are available; let them  bring charges against one another. But if you want anything beyond this, it shall be settled in the lawful assembly” (Acts 19:38–39).

Because he represents the God-ordained institution of civil government, a civil official is actually a minister of God, regardless of his personal beliefs about or relation to God. He is doing the Lord’s work whether he realizes it or not, by promoting peace and safety among men.

Robert Haldane comments that

The institution of civil government is a dispensation of mercy, and its existence is so indispensable, that the moment it ceases under one form, it reestablishes itself in another. The world, ever since the fall, when the dominion of one part of the human race over another was immediately introduced (Gen. 3:16), has been in such a state of corruption and depravity, that without the powerful obstacle presented by civil government to the selfish and malignant passions of men, it would be better to live among the beasts of the forest than in human society. As soon as its restraints are removed, man shows himself in his real character. When there was no king in Israel, and every man did that which was right in his own eyes, we see in the last three chapters of the Book of Judges what were the dreadful consequences. (An Exposition of Romans, 581)

In order to promote and protect the good in society, human government must punish the evil. Consequently, those who do what is evil have reason to be afraid.

Because the sword is an instrument of death, the weapon here symbolizes the right of civil government to inflict punishment, including the ultimate penalty of death for crimes that deserve it. In the earliest period of human existence, the Lord instituted capital punishment. “Whoever sheds man’s blood, by man his blood shall be shed, for in the image of God He made man” (Gen. 9:6). When Jesus told Peter, “Put your sword back into its place; for all those who take up the sword shall perish by the sword” (Matt. 26:52), he was reminding His disciple that the penalty for his killing one of Jesus’ enemies would be to perish himself through execution, which the Lord here acknowledges would be justified.

When Paul stood before the Roman governor Festus and made his appeal to Caesar, he said, “If then I am a wrongdoer, and have committed anything worthy of death, I do not refuse to die” (Acts 25:11). In saying that, he acknowledged that capital punishment was sometimes justified and that he would willingly accept it if he were to be found guilty of a capital crime.

Robert Culver again reminds us:

What must not be lost sight of is that, unpleasant as is the task of the jailor and the use of the whip, the cell, the noose, the guillotine, these things stand behind the stability of civilized society, and they stand there necessarily, for God has declared it so, in harmony with reality, rather than with apostate sociological opinion. Government, with its coercive powers, is a social necessity, but one determined by the Creator, not by the statistical tables of some university social research staff! No society can successfully vote fines, imprisonment, corporal and capital punishment away permanently. The society which tries has lost touch with realities of man (his fallen sinful state), realities of the world, and the truth of divine revelation in nature, man’s conscience, and the Bible. (Toward a Biblical View of Civil Government, 256)

When a society rejects capital punishment for even the most serious crimes, including murder, it comes under blood guiltiness from God. After Cain killed Abel, “The Lord said to Cain, ‘Where is Abel your brother?’ And he said, ‘I do not know. Am I my brother’s keeper?’ And He said, ‘What have you done? The voice of your brother’s blood is crying to Me from the ground’ ” (Gen. 4:10). Like Satan, whom he unknowingly had come to serve, Cain was both a murderer and a liar (see John 8:44). Immediately after the Flood, God established the divine law of capital punishment for murder (Gen. 9:6). As part of the Mosaic law, God declared, “You shall not pollute the land in which you are; for blood pollutes the land and no expiation can be made for the land for the blood that is shed on it, except by the blood of him who shed it” (Num. 35:33).

Among other things, Israel was sent into Babylonian captivity because of the many bloody crimes in the nation that went unpunished. “Make the chain,” God said, “for the land is full of bloody crimes, and the city is full of violence. Therefore, I shall bring the worst of the nations, and they will possess their houses. I shall also make the pride of the strong ones cease, and their holy places will be profaned” (Ezek. 7:23–24). When a nation does not administer justice, it eventually falls under God’s justice.

Abortion is murder of unborn children, and a nation that permits and even encourages this ghastly execution of the most innocent and helpless of those created in God’s image cannot possibly escape His  judgment. The land cries out for the blood of the millions upon millions of massacred babies. God will answer.