Why must He also be true God?

Heidelberg Catechism

Question 17. Why must He also be true God?

Answer. That by the power of His Godhead[1] He might bear in His manhood the burden of God’s wrath,[2] and so obtain for[3] 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