Christ and His Threefold Office by John Flavel and published by Reformation Heritage Books.
Flavel explores the glory of Christ becoming a man "to qualify and prepare Him for a full discharge of His mediatorship, in the office of our Prophet, Priest, and King."
"Salvation," says Flavel, "is revealed by Christ as a Prophet, procured by Him as a Priest, applied by Him as a King. In vain it is revealed, if not purchased; in vain revealed and purchased, if not applied."