“Duty” is a word that has been used throughout history in the positive sense of the term. From soldiers to civil servants to police officers to doctors to common laborers, many people have done their tasks because they believed it was their duty to do so. This sense of duty is usually a good thing.
It is also good and proper for Christians to talk about duty. Even though I haven’t come across this term in many recent Christian books, “duty” is a word Christians can and should use. “Duty” is a word used in the best sense of the term by many Christians in the past.
For one example, John Owen wrote a book called “The Grace and Duty of Being Spiritually Minded” (it’s found in volume 7 of his Works). In this book, he (obviously!) talks a lot about Christian duty.
Here’s what Owen notes about the duty of prayer (emphasis mine):
A person indisposed and lifeless, engaging unto prayer in a way of obedience, upon conviction of duty, may, in and by the gift, have his affections excited and grace engaged unto its proper work (p. 296).
Concerning Christian duty and superstition, he wrote,
And we are not forgo our duty because other men have been mistaken in theirs, nor part with practical, fundamental principles of religion because they have been abused by superstition (p. 346).
Wherefore, we are to call in all constraining motives, such as the consideration of the love of Christ, 2 Cor. 5:14, to keep the mind steady unto its duty (p. 386).
As you value your souls, defer not the duty you are called unto one moment (p. 466).
The Reformed Creeds and Confessions also speak about Christian duty. The Belgic Confession (Art. 36) says it is the “bounden duty” of Christians to “subject themselves to the magistrates.” The Canons of Dort (III/IV.15) says it is the Christian’s “duty” to pray for unbelievers whom God has not [yet] called. The Heidelberg Catechism notes that Christians have a “duty” to use their gifts to serve others and the Catechism says the church has a “duty” to excommunicate unrepentant sinners (Q/A 55, 82).
The Westminster Standards use the term “duty” over 20 times, mostly in terms of the Christian’s responsibility to obey God’s law: “What are the duties required in the 1st, 2nd, (etc.) commandment?” And the answers list scores of duties the Christians have with relation to obeying the Lord. The Westminster Confession even talks about the “conscience of duty” that the Spirit works in a believer (XVIII.4).
And, of course, our ultimate authority (Scripture) talks about duty. The kings and priests in the Old Testament had duties (1 Sam. 10:25, Num. 8:26). And Ecclesiastes straightforwardly says, “Fear God and keep his commandments, for this is the whole duty of man” (Ecc. 12:13).
There is more to this discussion about duty (e.g. God’s enabling grace, motives, ends, etc.), but we shouldn’t shy away from having a sense of duty as Christians. I have a Christian duty to love/care for my wife and children, to faithfully serve as a pastor to God’s people here, to regularly attend worship services, to help and love my neighbors, to be a good citizen of my country, and, above all, I have a duty to follow the Lord Jesus. It is not wrong to go to church out of a sense of duty, to pray out of a sense of duty, and to help your neighbor based on a sense of duty! There is a right and proper way to speak and think about Christian duty.
The above quotes from Owen are found in The Works of John Owen, ed. William H. Goold, vol. 7 (Edinburgh: T&T Clark, n.d.).