God was pleased, in his eternal purpose, to choose and ordain the Lord Jesus, his only begotten Son, according to the covenant made between them, to be the mediator between God and humanity (Isa 42:1; 1Pe 1:19-20). God chose him to be prophet (Ac 3:22), priest (Heb 5:5-6), and king (Ps 2:6; Lk 1:33), and to be head and savior of the church (Eph 1:22-23), the heir of all things (Heb 1:2), and judge of the world (Ac 17:31). From all eternity, God gave to the Son a people to be his offspring. In time these people would be redeemed, called, justified, sanctified, and glorified by him (Isa 53:10; Jn 17:6; Ro 8:30).
The Son of God, the second person of the Holy Trinity, is truly and eternally God. He is the brightness of the Father’s glory, the same in substance and equal with him. He made the world and sustains and governs everything he has made. When the fullness of time came, he took upon himself human nature, with all the essential properties and common weaknesses of it (Jn 1:14; Gal 4:4) but without sin (Ro 8:3; Heb 2:14, 16-17; 4:15). He was conceived by the Holy Spirit in the womb of the Virgin Mary. The Holy Spirit came down upon her, and the power of the Most High overshadowed her. Thus, he was born of a woman from the tribe of Judah, a descendant of Abraham and David in fulfillment of the Scriptures (Mt 1:22-23; Lk 1:27, 31, 35). Two whole, perfect, and distinct natures were inseparably joined together in one person, without converting one into the other or mixing them together to produce a different or blended nature. This person is truly God and truly man, yet one Christ, the only mediator between God and humanity (Ro 9:5; 1Ti 2:5).
The Lord Jesus, in his human nature united in this way to the divine in the person of the Son, was sanctified and anointed with the Holy Spirit beyond measure (Ps 45:7; Ac 10:38; Jn 3:34). He had in himself all the treasures of wisdom and knowledge (Col 2:3). The Father was pleased to make all fullness dwell in him (Col 1:19) so that—being holy, harmless, undefiled (Heb 7:26), and full of grace and truth (Jn 1:14)—he was thoroughly qualified to carry out the office of mediator and guarantor (Heb 7:22). He did not take this office upon himself but was called to it by his Father (Heb 5:5), who put all power and judgment in his hand and commanded him to carry them out (Jn 5:22, 27; Mt 28:18; Ac 2:36).
The Lord Jesus most willingly undertook this office (Ps 40:7-8; Heb 10:5-10; Jn 10:18). To discharge it, he was born under the law (Gal 4:4; Mt 3:15) and perfectly fulfilled it. He also experienced the punishment that we deserved and that we should have endured and suffered (Gal 3:13; Isa 53:6; 1Pe 3:18). He was made sin and a curse for us (2Co 5:21). He endured extremely heavy sorrows in his soul and extremely painful sufferings in his body (Mt 26:37-38; 27:46; Lk 22:44). He was crucified and died and remained in a state of death, yet his body did not decay (Ac 13:37). On the third day he arose from the dead (1Co 15:3-4) with the same body in which he suffered (Jn 20:25, 27). In this body he also ascended into heaven (Ac 1:9-11), where he sits at the right hand of his Father, interceding (Ro 8:34; Heb 9:24). He will return to judge men and angels at the end of the age (Ac 10:42; Ro 14:9-10; Ac 1:11; 2Pe 2:4).
The Lord Jesus has fully satisfied the justice of God, obtained reconciliation, and purchased an everlasting inheritance in the kingdom of heaven for all those given to him by the Father (Jn 17:2; Heb 9:15). He has accomplished these things by his perfect obedience and sacrifice of himself, which he once for all offered up to God through the eternal Spirit (Heb 9:14; 10:14; Ro 3:25-26).
The price of redemption was not actually paid by Christ until after his incarnation. Yet the virtue, efficacy, and benefit of it was imparted to the elect in every age since the beginning of the world, in and by those promises, types, and sacrifices that revealed him and pointed to him as the seed that would bruise the serpent’s head (1Co 4:10; Heb 4:2; 1Pe 1:10-11) and the Lamb slain from the foundation of the world (Rev 13:8). He is the same yesterday and today and forever (Heb 13:8).
In his work of mediation, Christ acts according to both natures, by each nature doing what is appropriate to itself. Even so, because of the unity of the person, that which is appropriate to one nature is sometimes in Scripture attributed to the person under the designation of the other nature (Jn 3:13; Ac 20:28).
To all those for whom Christ has obtained eternal redemption, he certainly and effectually applies and imparts it. He intercedes for them (Jn 6:37; 10:15-16; 17:9; Ro 5:10), unites them to himself by his Spirit, and reveals to them in and by his Word the mystery of salvation. He persuades them to believe and obey (Jn 17:6; Eph 1:9; 1Jn 5:20) and governs their hearts by his Word and Spirit (Ro 8:9, 14). He overcomes all their enemies by his almighty power and wisdom (Ps 110:1; 1Co 15:25-26), using methods and ways that are perfectly consistent with his wonderful and unsearchable governance. All these things are by free and absolute grace, apart from any condition for obtaining it that is foreseen in them (Jn 3:8; Eph 1:8).
This office of mediator between God and humanity is appropriate for Christ alone, who is the prophet, priest, and king of the church of God. This office may not be transferred from him to anyone else, either in whole or in part (1Ti 2:5).
The number and character of these offices is essential. Because we are ignorant, we need his prophetic office (Jn 1:18). Because we are alienated from God and imperfect in the best of our service, we need his priestly office to reconcile us and present us to God as acceptable (Col 1:21; Gal 5:17). Because we are hostile and utterly unable to return to God, and so that we can be rescued and made secure from our spiritual enemies, we need his kingly office to convince, subdue, draw, sustain, deliver, and preserve us for his heavenly kingdom (Jn 16:8; Ps 110:3; Lk 1:74-75).