The answer to this question may change depending on one’s understanding of minister. If understood broadly, any Christian may serve others. However, minister usually means someone whom Lutherans commonly call a pastor today. Therefore, obviously, every Christian is not a minister or pastor. In 1530 the first Lutherans understood this well when they confessed, “…no one should publicly teach in the Church or administer the Sacraments unless he be regularly called.”  It is possible to further explain the Augsburg Confession through an examination of the contemporary writings of Martin Luther related to this subject.
Early in the Reformation Luther made the biblical distinction between baptized priests and ministers when he wrote:
“For thus it is written I Pet. 2 [:9]: ‘You are a chosen race, a royal priesthood, and a priestly royalty.’ Therefore we are all priests, as many of us are Christians. But the priests, as we call them, are ministers chosen from among us. All they do is done in our name; the priesthood is nothing but a ministry. This we learn from I. Cor. 4 [:1]: ‘This is how one should regard us, as servants of Christ and stewards of the mysteries of God.’ ”
While Luther delineated between Christians as baptized priests and ministers, he did this to contrast the biblical office of preaching with the corrupt priesthood established through Roman episcopal ordination. Therefore, he asserted that papal priests had forsaken preaching the Word for praying the canonical hours and offering masses in propitiation for sins. In other words, he contrasted the Office of the Holy Ministry (Predigtamt, ministerium) with the papal priesthood. Additionally, Luther argues against the papal bishops’ claim that they alone had the authority to ordain pastors. Thereby, he rejected the Roman sacrament of ordination and the notion that pastors possessed an “indelible character” as a result of their ordination.
Luther’s rejection of Roman sacerdotal (priestly) authority did not mean the rejection of the pastoral office. During the 1520s new groups emerged that rejected the external call of ministers and the sacraments. Anabaptist preachers began to appear throughout Germany who claimed divine inspiration for their secret preaching. They also rejected infant baptism and the idea of the Christ’s physical presence in the Lord’s Supper. For this reason, in 1530 Lutherans condemned the Anabaptists as they confessed “That we may obtain this faith, the Ministry of Teaching the Gospel and administering the Sacraments was instituted.”
In the early 1530s Luther examined the nature of this ministry and the call of pastors in various writings. He specifically rejected wandering, secret preachers and affirmed the pastoral office when he stated, “For to the pastor is committed the pulpit, baptism, the sacrament [of the altar], and he is charged with the care of souls.” He then instructed faithful Christians to report these sneaky, uncalled preachers to their pastors. If these infiltrators did not have a call to preach, then Luther instructed them to be silent because they did not have a call to the pastoral office.
Dr. Luther included a lengthy discussion of the doctrine of the call in his lectures on Galatians in 1531 (published in 1535). He stated that every minister must be certain that his call is from God. While Christ called the apostles without means, God continues to call pastors through human means. In the sixteenth century city officials or princes often called pastors to certain parishes. (In twenty-first-century America, Christian congregations normally call pastors.) However, this call was no less divine than the apostles’ call. Luther made it clear that even if someone taught true doctrine, if he did not have a proper call, he should be told to stop preaching. He concluded, “Therefore we who are in the ministry of the Word have this comfort, that we have a heavenly and holy office; being legitimately called to this, we prevail over all the gates of hell.” It was necessary for a minister to boast in his call to glorify God, give him divine confidence in his ministry, and to give assurance to his congregation. Instead of puffing the pastor up this knowledge should humble him.
If all Christians are not ministers, then how should Christians live? According to Luther, the universal call is baptism and faith in Christ. Then, Christians, as baptized priests, serve their neighbors in love through various callings. Luther purposely contrasted the call to ordinary living in faith to monks whose external works only appeared spiritual. The world considers self-chosen religious activity as a true service to God. However, Luther responded that a servant’s cooking and housework is a service to God that surpasses monastic holiness. In the same manner that a pastor serves God through fulfillment of the duties of his call, the servant girl may joyfully serve God through completing her daily tasks.
Luther spoke similarly in numerous sermons and lectures. While commenting on Galatians 6:4, he referred to a Christian’s work as a divine calling whether he or she was a city leader, a servant, a teacher, or a student. Each person should fulfill his or her duties and not be concerned with others’ vocations. In a Christmas sermon Luther emphasized the deception of external appearances. Priests, monks, and friars seem holier than people who marry and work ordinary jobs. In fact, a baptized woman, who believes in Christ and lives ordinarily with her husband and children, is holier before God than a nun who exhibits great outward piety. Luther encouraged his hearers to demonstrate the fruits of faith in their daily callings.
According to Luther, every Christian is definitely not a minister. God calls pastors to do certain things because of their office. All Christians are not called to do those things, namely, preach God’s Word publicly or administer the sacraments. However, every Christian is a baptized priest, who by faith in Christ serves his neighbor in love through his or her divine vocations. This may be in the form of overt religious activity such as prayer, exhortation, or the comforting Word of the Gospel. However, taking out the trash also fulfills a vocation when done in faith, and is therefore a divine work too.
 Augsburg Confession, art. 14. http://www.bookofconcord.org/augsburgconfession.php#article14
 Martin Luther, The Babylonian Captivity of the Church, Luther’s Works 36: 112-13. [Emphasis added]
 Ibid., 113-116; Norman Nagel, “Luther and the Priesthood of All Believers,” CTQ 61 (1997): 284-285, 289. http://ctsfw.net/media/pdfs/nagelnlutherpriesthoodallbelievers.pdf.
 Augsburg Confession, art. 5. http://www.bookofconcord.org/augsburgconfession.php#article5 . The Latin text refers to the ministerium and the German uses the term, Predigtamt which literally means preaching office. Concordia Triglotta, (St Louis 1921), 44. The English text is a translation of the Latin version.
 Martin Luther, “Infiltrating and Clandestine Preachers,” Luther’s Works 40: 384-87. (Quote on p. 384)
 Idem, “Lectures on Galatians (1535),” Luther’s Works 26: 19-21 (Quote on p. 20). [Emphasis added]
 Idem, “Lectures on Genesis,” Luther’s Works 3: 131.
 Idem, “Sermon for Fifteenth Sunday After Trinity,” The House Postils, vol. 3, ed. Eugene Klug (Grand Rapids 1996), 10-11.
 Idem, “Lectures on Galatians (1535),” Luther’s Works 27: 119-120.
 Idem, “Third Sermon for the Festival of Christ’s Nativity,” House Postils 3: 232-233.