The teaching in the Westminster Confession of Faith and the Shorter and Larger Catechism on the offices of Christ help understand Christ ministry on earth and what He is doing in heaven. Christ fulfills three offices, the offices of Prophet, Priest, and King.
His office as Mediator is his once offering himself a sacrifice without spot to God, To be a reconciliation for the sins of his people for all time; In making continual intercession for them.
His office as Prophet is 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 salvation.
His office as King is His bestowing saving grace upon his elect giving them officers, laws, and censures, by which he visibly governs them, ordering all things for his own glory, and taking vengeance on the rest, who know not God.
