I do not Frustrate the Grace of God

16 Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified. 17 But if, while we seek to be justified by Christ, we ourselves also are found sinners, is therefore Christ the minister of sin? God forbid. 18 For if I build again the things which I destroyed, I make myself a transgressor. 19 For I through the law am dead to the law, that I might live unto God. 20 I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me. 21 I do not frustrate the grace of God: for if righteousness come by the law, then Christ is dead in vain. Galatians 2:16-21