(c) even the best works of believers are polluted with sin. Moreover, Scripture teaches us very clearly that man is justified freely by the grace of God, Rom. 3:24, and that he cannot possibly be justified by the works of the law, Rom. 3:28; Gal. 2:16; 3:11.
2. Positively, that the ground of justification can be found only in the perfect righteousness of Jesus Christ, which is imputed to the sinner in justification. This is plainly taught in several passages of Scripture, such as Rom. 3:24; 5:9,19; 8:1; 10:4; 1 Cor. 1:30; 6:11, 11Cor. 5:21; Phil. 3:9. In the passive obedience of Christ, who became a curse for us (Gal. 3:13) we find the ground for the forgiveness of sins; and in His active obedience, by which He merited all the gifts of grace, including eternal life, the ground for the adoption of children, by which sinners are constituted heirs of life eternal. The Arminian goes contrary to Scripture when he maintains that we are accepted in favor by God only on the ground of our faith or evangelical obedience.
Louis Berkhof, Systematic Theology, 523.