The Covenant of Redemption (Pactum Salutis)
The eternal intra-Trinitarian covenant in which the Father appoints the Son as Mediator and the Son freely accepts the office for the elect. The Standards affirm its substance (WCF VIII.1; LC Q. 31) without the developed tri-covenantal apparatus of Cocceius or Witsius. The pactum salutis grounds the unity of the decree and the covenant.
Westminster Confession
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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 Saviour 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.
Larger Catechism
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The covenant of grace was made with Christ as the second Adam, and in him with all the elect as his seed.
Sum of Saving Knowledge
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Head II. The remedy provided in Jesus Christ for the elect by the covenant of Grace §2 →
The sum of the covenant of redemption is this: God having freely chosen to life a certain number of lost mankind, for the glory of his rich grace, did give them, before the world began, to God the Son, appointed Redeemer, that, upon condition he would humble himself so far as to assume the human nature, of a soul and a body, to personal union with his divine nature, and submit himself to the law, as surety for them, and satisfy justice for them, by giving obedience in their name, even to the suffering of the cursed death of the cross, he should ransom and redeem them all from sin and death, and purchase to them righteousness and eternal life, with all saving graces leading thereto, to be effectually, by means of his own appointment, applied in due time to every one of them.
For the accomplishment of this covenant of redemption, and making the elect partakers of the benefits of it in the covenant of grace, Christ Jesus was clad with the threefold office of Prophet, Priest, and King: made a Prophet, to reveal all saving knowledge to his people, and persuade them to believe and obey the same; made a Priest, to offer up himself a sacrifice once for them all, and to intercede continually with the Father, for making their persons and services acceptable to him; and made a King, to subdue them to himself, to feed and rule them by his own appointed ordinances, and to defend them from their enemies.