Romans 15:16

That I should be the minister of Jesus Christ
The office of apostleship is here amplified and enlarged on, and the ends shown for which that grace was given to him, that he should be a minister; not in holy things about the temple, as the priests and Levites were; or a teacher of the law, some were fond of; but a minister of Christ, one that was made so by him, was qualified and sent forth to minister in his name to men; and who was a preacher of him; Jesus Christ, and him crucified, was the grand subject of his ministrations; he adds,

to the Gentiles;
for to them, though not to the exclusion of the Jews, was he appointed a minister by Christ, and sent by him to them; among them he chiefly ministered, and was particularly and eminently useful to them; and this is another reason why the Romans ought to bear with a little boldness and freedom in writing to them, since he was the apostle of the Gentiles:

ministering the Gospel of God;
not the service of the temple, nor the traditions of the elders, nor the law of Moses, nor the morality of the Heathens; but the Gospel, of which God is the author, whose grace is the subject, and whose glory is the end; and is good news from him to the chief of sinners; to the preaching of which the apostle was separated by him:

that the offering up of the Gentiles;
not the offering the Gentiles offered up, their prayers, praises, or good works, though these are acceptable to God through Christ; but the Gentiles themselves, by the offering up of whom is meant their conversion; which was the end of the apostle's ministering the Gospel among them, and in which he was the happy instrument. The allusion is to the priests slaying and offering up sacrifices under the law. The apostle was a priest in a figurative and improper sense; the sacrifices he offered up were not slain beasts, but men, the Gentiles, cut to the heart by the sword of the Spirit, the ministry of the Gospel; whose inside being laid open to them, and they brought to a sense of their lost condition, and need of Christ, were, through the power of divine grace attending the word, made willing to offer, or give up themselves to the Lord, to be saved by him, and him only: this the apostle, as an instrument, was concerned in; and all his view was, that it

might be acceptable;
that is, to God, as nothing is more so to him than a broken and a contrite heart, or souls brought to a sense of themselves; and to believe in Christ, and submit to his righteousness; and then both ministers and converts are unto God, a sweet savour of Christ:

being sanctified by the Holy Ghost;
this is said in allusion to the washing of the sacrifices under the law; and intimates, that the Gentiles, though unclean by nature and practice, yet being sanctified by the Spirit of God, whose proper work it is to sanctify, become an acceptable, being an holy sacrifice to an holy God.