John Murray on the necessity of Christ's righteousness and atonement

Salvation requires not only the forgiveness of sin but also justification. And justification, adequate to the situation in which lost mankind is, demands a righteousness such as belongs to no other than the incarnate Son of God, a righteousness undefiled and undefilable, a righteousness with divine property and quality (cf. Rom. 1:17; 3:21; 22; 10:3; II Cor. 5:21; Phil. 3:9). It is the righteousness of the obedience of Christ (Rom. 5:19). But only the Son of God. incarnate, fulfilling to the full extent the commitments of the Father's will, could have provided such a righteousness. A concept of salvation bereft of the justification which this righteousness imparts is an abstraction of which Scripture knows nothing. (John Murray, The Atonement)