Rom 15:15-16 is a difficult passage for many Protestants who reject the doctrine that there is a ministerial New Covenant Priesthood, one independent from the so-called "Priesthood of All believers," as Paul, without any qualifications and hesitation, applies priestly language to his cultic activities. The NIV, a popular Evangelical translation, renders the text thusly:
Yet I have written you quite boldly on some points to remind you of them again, because of the grace God gave me to be a minister of Christ Jesus to the Gentiles. He gave me the priestly duty of proclaiming the gospel of God, so that the Gentiles might become an offering acceptable to God, sanctified by the Holy Spirit.
That Protestants have a difficult time with this passage can be seen from the humming and hawing by one Reformed scholar in a book-length treatment of the theology of priesthood in the Bible:
. . . Paul has no compunction in applying the language [of priesthood] to himself, and we can reasonably concur with Donald Robinson ('The Priesthood of Paul in the Gospel of Hope,' in R.J. Banks, ed. Reconciliation and Hope: New Testament Essays on Atonement and Eschatology [Paternoster, 1974], 231) that ‘In this cult the god is Jesus Christ, and Paul is his leitourgos i.e., the priest.’
As Hank Voss notes (The Priesthood of All Believers and the Missio Dei: A Canonical, Catholic, and Contextual Perspective [Pickwick, 2016], 8, 43), this should surprise us. As all an avid student and teacher of Scripture, Paul from the tribe of Benjamin might be hesitant to associate himself with the cultic prerogatives of Levi’s tribe, even in a metaphorical comparison. Perhaps, then, Paul like Hebrews is starting to realize that the old order of Levitical priesthood is coming to an end (James D.G. Dunn, Romans [WBC; 2 vols; Waco, Tex.: 1988], 859-861). Although Paul does not spell out his precise priestly responsibilities, it is commonly understood—and consistent with his ministry in Romans and beyond—that he emphasizes the work of bringing outsiders closer to God, especially through a ministry of teaching or proclamation (e.g., NIV, NCV; Robinson 1974:231-232; C.G. Kruse, Paul's Letter to the Romans [PNTC; Eerdmans, 2012], 538; R.N. Longenecker, The Epistle to the Romans [NIGTC; Eerdmans, 2016], 1036). And if Paul has in mind here a passage such as Isaiah 66:20 (Dunn 1988:860; T.R. Schreiner, Romans [BECNT; Baker, 1998], 767), this is both consistent with and an extension of those closing chapters of Isaiah. There the Gentiles would restore God’s Israelite people to God, but now these Gentiles are themselves counted as gifts to God and thence servants of God! Romans joins Isaiah and 1 Peter and Revelation in using once exclusive cultic imagery to celebrate the inclusion of Gentile worship. (Andrew S. Malone, God’s Mediators: A biblical theology of priesthood [New Studies in Biblical Theology 43; London: Apollos, 2017], 161, emphasis added, comment in square bracket added for clarification)
For those who wish to see the evidence for the existence of an ordained, ministerial New Covenant Priesthood, be sure to pick up a copy of my book:
After the Order of the Son of God: The Biblical and Historical Evidence for Latter-day Saint Theology of the Priesthood (2018). The following comes from pp. 99-105 which discusses, in part, Rom 15:15-16, sowing that this passage (and many others) teaches a New Covenant Priesthood:
Finally, that the apostle Paul held to a high ecclesiology can be seen in his other writings. As Jimmy Akin noted ("The Priesthood Debate" URL: http://www.ewtn.com/library/ANSWERS/PRIEST3.htm):
b. 2 Tim 1:6
We find the same pattern in 2 Timothy 1:6, when Paul urges his protégé to fulfill his ministry and says: "I remind you to rekindle the gift of God that is within you through the laying on of my hands."
c. 1 Tim 4:14
He spoke of the same thing in 1 Timothy 4:14, where Paul explains how he must fulfill his ministry as an evangelist and tells him: "Do not neglect the gift you have, which was given you by prophetic utterance when the council of elders laid their hands upon you."
Other translators render this "which was given you . . . with the laying on of hands for the presbytery" or "in order to become a member of the presbytery."
d. 1 Tim. 5:19-22: Pass it on!
This gift of the Holy Spirit, through the laying on of hands in ordination, was something Paul instructed Timothy to pass on in the future. Part of his duty as a bishop-evangelist was to ordain elders in different congregations. He tells Timothy he must exercise this ministry carefully, lest he ordain a priest unworthy of the office. In 1 Timothy 5:19-22 he tells the young evangelist: "Never admit any charge against an elder except on the evidence of two or three witnesses. As for those who persist in sin, rebuke them in the presence of all, so that the rest may stand in fear. . . . Do not be hasty in the laying on of hands, nor participate in another man's sins; keep yourself pure."
Paul tells Timothy not to lay hands on an elder too quickly; don't ordain him until he has been tested and shown to be of excellent character. Otherwise Timothy will share in his sins.
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a. The priestly duty of preaching
i. Rom 15:15-16
The Bible indicates New Testament priests offer at least two sacrifices. One of them is discussed in Romans 15:15-16. In the New International Version of this passage, we read:
"I have written you quite boldly on some points, as if to remind you of them again, because of the grace God gave me to be a minister of Christ Jesus to the Gentiles with the priestly duty of proclaiming the gospel of God, so that the Gentiles might become an offering acceptable to God, sanctified by the Holy Spirit."
Paul tells us that because he has been given a calling as a professional minister of Christ, he has a priestly duty of preaching the gospel so that the Gentiles may be an offering—a sacrifice to God
As Akin correctly notes about Rom 15:16, Paul uses a term which shows that he understood himself to be engaging in priestly, cultic activity:
To be a minister (λειτουργός) of Christ Jesus to the Gentiles. He gave me the priestly duty (ἱερουργέω) of proclaiming the gospel of God, so that the Gentiles might become an offering (προσφορὰ) acceptable to God, sanctified by the Holy Spirit. (NIV)
Paul, in this verse, couples the noun λειτουργός (“minister”; we derive the term “liturgy” [how religious worship is conducted] from this Greek word) with the verb ἱερουργέω, “to act as a priest.” As James Dunn notes:
εἰς τὸ εἶναί με λειτουργὸν Χριστοῦ Ἰησοῦ εἰς τὰ ἔθνη, “in order that I might be a minister of Christ Jesus for the Gentiles.” Although λειτουργός can mean merely “servant,” as most often in the LXX (Josh 1:1; 2 Sam 13:18; 1 Kgs 10:5; etc.; see further on 13:6), almost certainly Paul has in mind here the more specific cultic sense (“priest”), as in Neh 10:39; Isa 61:6; Sir 7:30; and as in Heb 8:2 and 1 Clem. 41:2; the cultic language of the following clauses puts this almost beyond dispute (so, e.g., TDNT 4:230; Spicq, 480; Lietzmann; Barrett; Schlier; and Wilckens; Hultgren, Gospel, 134-35, refers particularly to Sir 50:12-13). (James D.G. Dunn, Romans 9-16 [Word Biblical Commentary vol. 38B; Nashville: Thomas Nelson, 1988], 859, emphasis added)
With respect to ἱερουργέω, BDAG, referencing Rom 15:16, defines the verb thusly:
3681 ἱερουργέω
• ἱερουργέω (ἱερουργός ‘sacrificing priest’; Plut., Num. 14, 1, Alex. 31, 4; Herodian 5, 6, 1; 5, 5, 9; Philostrat., Vi. Soph. 2, 10, 2 p. 91, 25; CIG add. to 4528 [III p. 1175]; IG2 I, 4, 4f; 8 [V BC]; 4 Macc 7:8 v.l.; Philo, Mos. 1, 87 al.; Jos., Ant. 6, 102; 7, 333) to act in some cultic or sacred capacity, perform holy service, act as a priest τὶ w. regard to someth. τὸ εὐαγγέλιον serve the gospel as a priest (perh. w. emphasis on sacrifice; Field, Notes 165) Ro 15:16. —DELG s.v. ἱερός. M-M. TW.
As Greek grammarian Max Zerwick put it succinctly, Paul is:
[Serving] in the capacity of a priest.” (Max Zerwick, A Grammatical Analysis of the Greek New Testament [rev ed.; trans. Mary Grosvenor; Rome: Biblical Institute Press, 1981], 493, comment in square bracket added for clarification)
Finally, these terms are coupled with the Greek noun προσφορὰ, a noun denoting gifts/offerings to a deity. As BDAG, again referencing Rom 15:16, notes:
6352 προσφορά
• προσφορά, ᾶς, ἡ (προσφέρω; Soph.+; pap, LXX; TestLevi 3:6; 14:5; EpArist 170; Joseph., Just.; Hippol., Ref. 6, 16, 2)
1. the act of bringing as a voluntary expression (‘presenting, offering’: Pla., Aristot., Polyb.; Did., Gen. 125, 8), in our lit. in the literal as well as fig. sense of sacrificing, offering (Sir 46:16 προσφορὰ ἀρνός) foll. by the obj. gen. διὰ τῆς προσφορᾶς τοῦ σώματος Ἰησοῦ through the offering of Jesus’ body in sacrifice Hb 10:10. Cp. vss. 14, 18 (s. Windisch, Hdb., exc. on Hb 10:18). προσφορὰς ποιεῖν have sacrifices made Ac 24:17; 1 Cl 40:4 (Just., D. 29, 8; 67, 8). W. λειτουργίαι vs. 2. ἀνθρωποποίητος πρ. an offering made by man B 2:6 (mng. 2 is also prob.). προσφορᾶς γενομένης ὑπὸ τοῦ Παύλου when a sacrifice had been made by Paul AcPl Ha 6, 37.
2. that which is brought as a voluntary expression (‘present, gift’: Theophr., Char. 30, 19) in our lit. in fig. and literal use offering (Sir 14:11; 34:18, 19 al.; TestLevi 14:5) w. ὁλοκαύτωμα MPol 14:1. W. θυσία Eph 5:2; Hb 10:5 (Ps 39:7). W. θυσίαι, ὁλοκαυτώματα κτλ. (s. Da 3:38; Jos., Ant. 11, 77) vs. 8 (Ps 39:7); B 2:4; ἀνθρωποποίητος προσφορά a sacrifice made by a human being vs. 6 (mng. 1 is also prob.; s. above). προσηνέχθη ἡ προσφορά Ac 21:26 (προσφέρω 2a). Jesus is called ὁ ἀρχιερεὺς τῶν προσφορῶν ἡμῶν the High Priest of our offerings in that he brings the prayers of the Christians into God’s presence 1 Cl 36:1. ἡ προσφορὰ τῶν ἐθνῶν the offering that consists of the gentiles (i.e. those from ‘the nations’ who have become Christian) Ro 15:16. For the interpretation of ἐθνῶν as subjective, the offering that the Gentiles make s. A-MDenis, RSPT 42, ’58, 405f.—DELG s.v. φέρω D. M-M. TW.
It is clear that Paul is presenting himself as a New Covenant Priest in this verse. Had Paul held to the Protestant conception of authority and priesthood, he would not have used what is such sloppy, misleading language, but it makes perfect sense if, in Paul’s theology, there exists a New Covenant Priesthood. As Catholic apologist, Trent Horn, noted:
Notice that Paul doesn’t refer to the laity as being fellow priests like him. Instead, they were a sacrifice that he and other ministers offered to God. According to the Protestant authors Rosalind Brown and Christopher Cocksworth,
Some Christians find this embarrassing and prefer to speak about ministers, pastors, and parsons, or are more comfortable with more occupational descriptions like vicar, rector, or chaplain . . . For our part we do not think that it is so easy to dismiss the nomenclature as a semantic mistake precisely because the presbyter’s ministry among the priestly people of God takes on certain priestly characteristics. (Rosalind Brown and Christopher Cocksworth, On Being a Priest Today [Cambridge, Mass.: Cowley Publications, 2004], 29-30)
(Trent Horn, The Case for Catholicism: Answers to Classic and Contemporary Protestant Objections [San Francisco: Ignatius Press, 2017], 143)