Question #114: But can those converted to God obey these commandments perfectly?
Answer: No. In this life even the holiest have only a small beginning of this obedience. Nevertheless, with all seriousness of purpose, they do begin to live according to all, not only some, of God's commandments (Eccles. 7:20; Rom. 7:14-15; 1 Cor. 13:9; 1 John 1:8-10; Ps. 1:1-2; Rom. 7:22-25; Phil. 3:12-16).
Question #115: No one in this life can obey the Ten Commandments perfectly: why then does God want them preached so pointedly?
Answer: First, so that the longer we live the more we may come to know our sinfulness and the more eagerly look to Christ for forgiveness of sins and righteousness. Second, so that, while praying to God for the grace of the Holy Spirit, we may never stop striving to be renewed more and more after God's image, until after this life we reach our goal:perfection (Ps. 32:5; Rom. 3:19-26; 7:7, 24-25; 1 John 1:9; 1 Cor. 9:24; Phil. 3:12-14; 1 John 3:1-3).