Verily, verily, I say unto you, Whosoever committeth sin is the servant of sin. – John 8:34
It is easy for all men and women by nature to place in the category of “servants of sin” all who are immoral, irreligious, and insincere. Such people whose lives and conduct are characterized by such sins are truly servants of sin. But Christ was speaking to moral, religious men who appeared righteous outwardly. It would be convenient for us to say simply that they were not sincere about their religion (and there probably were many of them who were not sincere), but, on the whole, the Pharisees were the most dedicated and most sincere. How could Christ say, then, that they were servants of sin? He was speaking of the sin that is common to all of us by nature and which deceives all of us by nature. Before God grants genuine God-given faith to a person as an object of His grace in Christ, that person is a servant of sin no matter what else may be said of him. He may be religious, sincere, dedicated, kind, humble (as the world sees it), charitable, but before salvation by God's grace in Christ, all of this is nothing more than "fruit unto death" (Rom. 7:5). Before we hear and believe God's Gospel, His declaration of eternal salvation and final glory conditioned on Christ alone, based on His righteousness alone, all we can do in religion and morality is try to establish a righteousness of our own (Rom. 10:1-3), and this is opposed to God's glory and Christ's pre-eminence in salvation. It is a denial of Christ and His Gospel. A servant of sin, then, is one who thinks that something other than the merits of Christ's obedience and death can in some way recommend him unto God. All unbelievers are servants of sin. Thank God He delivers His people from being servants of sin to being servants of righteousness (Rom. 6:17-18). A person who is by God's grace a servant of righteousness may have been just as moral and sincere before salvation as he is after salvation, but now his motive for being moral is different. Now, being a servant of righteousness, his motive is not legalism. His motive now is grace and gratitude – the assurance of all of salvation based on the righteousness of Christ according to God's grace and mercy.