Romans 15:14-16 — And I myself also am persuaded of you, my brethren, that ye also are full of goodness, filled with all knowledge, able also to admonish one another.
Nevertheless, brethren, I have written the more boldly unto you in some sort, as putting you in mind, because of the grace that is given to me of God,
That I should be the minister of Jesus Christ to the Gentiles, ministering the gospel of God, that the offering up of the Gentiles might be acceptable, being sanctified by the Holy Ghost.
goodness — not moral excellence, but a disposition to be kind to others
Goodness and knowledge are both necessary for admonition.
minister = priestly service
offering up = believers giving themselves
being sanctified = having been sanctified, by a divine act at the moment of salvation.
Paul is the priest by divine call. The believers are offering themselves as sacrifices. These sacrifices (believers) are cleansed by the Holy Spirit.