Q. Why was our Mediator called Christ?
A. Our Mediator was called Christ, because he was anointed with the Holy Ghost above measure, and so set apart, and fully furnished with all authority and ability, to execute the offices of prophet, priest, and king of his church, in the estate both of his humiliation and exaltation.
Q. How doth Christ execute the office of a prophet?
A. Christ executeth the office of a prophet, in his revealing to the church, in all ages, by his Spirit and Word, in divers ways of administration, the whole will of God, in all things concerning their edification and salvation.
(Questions XLII and XLIII of the Westminster Larger Catechism.)