(v 15) What then? Shall we sin because we are not under law but under grace? Certainly not!
This is the old question referred to in Ro 6:1. The trivial objection in Paul’s time, as well as in our time, was that grace, forgiveness of sin, was an encouragement to sin. Paul shows, with much emphasis, that this is a false charge, since grace, forgiveness, implied that the sinner had died to sin. It is those who have been freed from the dominion of sin who are delivered from its penalties.
(v. 16) Do you not know that to whom you present yourselves slaves to obey, you are that one’s slaves whom you obey, whether of sin leading to death, or of obedience leading to righteousness?
If we obey sin, we are sin’s servants, under his reign, and will receive, not grace, but sin’s wages, which is death; or, on the other hand, if we obey Christ, we are his servants, and enjoy his righteousness. None enjoy this blessedness but those who turn from sin and obey Christ.
(v. 17) But God be thanked that though you were slaves of sin, yet you obeyed from the heart that form of doctrine to which you were delivered
“But God be thanked” means that, having been sinners, they had become obedient to Christ.
“Obeyed from the heart” meaning that no outward obedience is of the slightest value unless the heart turns to God.
(v.18) “And having been set free from sin, you became slaves of righteousness.”
When we died to sin, and were buried into Christ (Ro 6:3). Hence, being no longer sin’s servants, we become servants of righteousness.
(v 19) “I speak in human terms because of the weakness of your flesh. For just as you presented your members as slaves of uncleanness, and of lawlessness leading to more lawlessness, so now present your members as slaves of righteousness for holiness.”
“I speak in human terms” means that Paul used figures taken from human relations — those of master and slave. At that time slavery existed everywhere.
As they had been servants of sin in its various forms, uncleanness, wickedness, so now being freed from that service, let them serve righteousness unto holiness, with the result of showing forth holy lives.
(v. 20) “For when you were slaves of sin, you were free in regard to righteousness”.
While servants of sin they did not serve righteousness at all.
( v.21) “What fruit did you have then in the things which you are now ashamed? For the end of those things is death.”
We ought to seriously ask this question. What fruit do the shameful practices of sin bring us? Only shame and death.
( v.22) “But now having been set free from sin, and having become slaves of God, you have your fruit to holiness, and the end, everlasting life.”
Now being freed from the bondage of sin, sin should not be served at all, because they have become servants of God. He has the right to their full service. The fruit borne should be holiness, holy lives. The end everlasting life. The result of the service of sin is death (Ro 6:21); but that of the service of God is everlasting life.
(v.23) “For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord.”
Sin is a master of his servants and pays wages. The wages is death, one of the saddest, but profoundest truths of the world. But the gift of God to those who turn from sin, life eternal. It is his gracious gift, conditioned on refusing to be the servant of sin longer, and is through Christ.
-From The People’s New Testament Commentary Of Romans 6:15-23