A magistrate ought not to let the sword of justice rust in the scabbard. As he should not let the sword be too sharp by severity, so neither should the edge of it is blunted by too much leniency [mercy].
The New Testament does not say that the death penalty is done away with nor does it say that we should implement the civil laws of God wherever we are. Rather, we are called to obey the rules of the land we’re living in as far as they are in accords to God’s law. Dr. Philip Ross observes:
…it is an unavoidable conclusion that rather than campaigning for Moses-inspired judicial reform, the epistles called upon Christians to submit themselves to nation laws that were not patterned on the judicial laws of Israel.
Something Greater Than The Death Penalty
Rather than soften the penalty for sin, in the New Testament, the clearer revelation is given of punishment after death. For example, in Hebrews 10:28-29, an argument is made by the author from the lesser to the greater. He says, under the Old Covenant, which has passed away, the person who has set aside the law of Moses or disregards Moses’ law is put to death. The sentence of death is brought upon the transgressor. He is put to death physically. But now the author, after giving the example of the lesser moves to the greater:
29 How much worse punishment do you think one will deserve who has trampled on the Son of God, regarded as profane the blood of the covenant by which he was sanctified, and insulted the Spirit of grace?
What is worse than physical death? The second death—eternal ruin and misery. The earthly and physical penalties are no longer binding, but that does not mean that God changed His morality. It only means that God will wait a little longer for the execution of His perfect justice. In these examples, which we see in Hebrews (e.g. Heb. 2:1-4; 10:28-29), we are warned on the basis of earthly penalties of the former covenant, of greater penalties of the one who despises Christ and His covenant.
1 Corinthians 9:7-10 And General Equity
1Cor. 9:7-10 Who serves as a soldier at his own expense? Who plants a vineyard without eating any of its fruit? Or who tends a flock without getting some of the milk? 8 Do I say these things on human authority? Does not the Law say the same? 9 For it is written in the Law of Moses, “You shall not muzzle an ox when it treads out the grain.” Is it for oxen that God is concerned? 10 Does he not certainly speak for our sake? It was written for our sake, because the plowman should plow in hope and the thresher thresh in hope of sharing in the crop.
Paul here cites a civil law (Deut. 25:4) concerning animals and gets the principle behind the law and th...