1. It pleased God, in his eternal purpose, to choose and ordain the Lord Jesus, his only begotten Son, to be the Mediator between God and man, the Prophet, Priest, and King, the Head and Savior of his church, the Heir of all things, and Judge of the world: unto whom he did from all eternity give a people, to be his seed, and to be by him in time redeemed, called, justified, sanctified, and glorified.
WLC Q&A – 41-45
Q. 41. Why was our mediator called Jesus?
A. Our mediator was called Jesus, because he saveth his people from their sins.
Q. 42. 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. 43. 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.
Q. 44. How doth Christ execute the office of a priest?
A. Christ executeth the office of a priest, in his once offering himself a sacrifice without spot to God, to be a reconciliation for the sins of the people; and in making continual intercession for them.
Q. 45. How doth Christ execute the office of a king?
A. Christ executeth the office of a king, in calling out of the world a people to himself, and giving them officers, laws, and censures, by which he visibly governs them; in bestowing saving grace upon his elect, rewarding their obedience, and correcting them for their sins, preserving and supporting them under all their temptations and sufferings, restraining and overcoming all their enemies, and powerfully ordering all things for his own glory, and their good; and also in taking vengeance on the rest, who know not God, and obey not the gospel.
WSC Q&A 23-26
Q. 23. What offices doth Christ execute as our redeemer?
A. Christ, as our redeemer, executeth the offices of a prophet, of a priest, and of a king, both in his estate of humiliation and exaltation.
Q. 24. How doth Christ execute the office of a prophet?
A. Christ executeth the office of a prophet, in revealing to us, by his word and Spirit, the will of God for our salvation.
Q. 25. How doth Christ execute the office of a priest?
A. Christ executeth the office of a priest, in his once offering up of himself a sacrifice to satisfy divine justice, and reconcile us to God; and in making continual intercession for us.
Q. 26. How doth Christ execute the office of a king?
A. Christ executeth the office of a king, in subduing us to himself, in ruling and defending us, and in restraining and conquering all his and our enemies.
Heidelberg Catechism Q&A 31
31. WHY IS HE CALLED “CHRIST, THAT IS, ANOINTED?
Because He is ordained of God the Father and anointed with the Holy Spirit to be our chief Prophet and Teacher, who has fully revealed to us the secret counsel and will of God concerning our redemption; and our only High Priest, who by the one sacrifice of His body, has redeemed us, and ever lives to make intercession for us with the Father; and our eternal King, who governs us by His Word and Spirit, and defends and preserves us in the redemption obtained for us.
 Ps 45:7 [Heb 1:9]; Isa 61:1 (Lk 3:21-22, 4:18);  Deut 18:15 (Acts 3:22);  Jn 1:18, 15:15;  Ps 110:4 (Heb 7:17, 21);  Heb 9:12, 10:11-14;  Rom 5:9-10, 8:34;Heb 9:24; 1 Jn 2:1;  Zech 9:9 (Mt 21:5); Lk 1:33;  Ps 2:6; Isa 61:1-2; Mt 28:18-20;Jn 10:28; 1 Pt 2:24; Rev 12:10-11, 19:16
Children’s Catechism Q&A 64-71
Q. 64. What offices has Christ?
A. Christ has three offices.
Q. 65. What are they?
A. The offices of a prophet, of a priest, and of a king.
Q. 66. How is Christ a prophet?
A. Because he teaches us the will of God.
Q. 67. How is Christ a priest?
A. Because he died for our sins and pleads with God for us.
Q. 68. How is Christ a king?
A. Because he rules over us and defends us.
Q. 69. Why do you need Christ as a prophet?
A. Because I am ignorant.
Q. 70. Why do you need Christ as a priest?
A. Because I am guilty.
Q. 71. Why do you need Christ as a king?
A. Because I am weak and helpless.