Heidelberg Catechism — Lord’s Day 6

16 Why must He be a true and righteous man?

Because the justice of God requires that the same human nature which has sinned should make satisfaction for sin;¹ but one who is himself a sinner cannot satisfy for others.² 

1. Rom 5:12, 15; 1 Cor 15:21; Heb 2:14-16; Isa 53:3-5; Heb 7:26-27; 1 Pt 3:18

17 Why must He also be true God?

That by the power of His Godhead¹ He might bear in His manhood the burden of God’s wrath,² and so obtain for³ and restore to us righteousness and life.⁴ 

1. Isa 9:5;
2. Dt 4:24; Isa 53:8; Ps 130:3; Nah 1:6; Acts 2:24;
3. Jn 3:16; Acts 20:28;
4. Isa 53:5, 11; 2 Cor 5:21; 1 Jn 1:2

18 But who now is that Mediator, who in one person is true God and also a true and righteous man?

Our Lord Jesus Christ,¹ who is freely given unto us for complete redemption and righteousness.² 

1. Mt 1:21-23; Lk 2:11; 1 Tim 2:5, 3:16;
2. Acts 4:12; 1 Cor 1:30

19 From where do you know this?

From the Holy Gospel, which God Himself first revealed in Paradise,¹ afterwards proclaimed by the holy patriarchs² and prophets,³ and foreshadowed by the sacrifices and other ceremonies of the law,⁴ and finally fulfilled by His well-beloved Son.⁵ 

1. Gen 3:15;
2. Gen 12:3, 22:18, 49:10-11;
3. Isa 53; Jer 23:5-6; Mic 7:18-20; Acts 3:22-24, 10:43; Rom 1:2; Heb 1:1;
4. Lev 1:7; Jn 5:46; Heb 10:1-10;
5. Rom 10:4; Gal 4:4-5; Col 2:17; Heb 10:1