Deuteronomy 6:25 And it shall be our righteousness, if we observe to do all these commandments before the Lord our God, as he hath commanded us.
Once again the response of believers to God’s Gospel is to observe to do all the Commandments of the Lord. We do them in the presence of (before) the Lord. When we are aware of God with us, and study and think about Him, we almost automatically do what we know pleases Him. And when we observe to do His Word we intentionally weigh the options of thought, speech, and action and choose to the do the right thing. We are guided by the Word and led by the Spirit.
However, we still remain sinners and many times fail to do. If we always did right in thought, word, and deed it would be our righteousness. But we don’t do right because we aren’t right. However Jesus Christ is our righteousness, and wisdom and sanctification and redemption (1 Cor. 1:30). Through faith we receive the righteousness of God earned for us by Christ. The active obedience of Christ is His innocent suffering and death. The passive obedience of Christ is His holy, righteous life. Both are substitutionary: He died for us and He lived for us.
Our response to such great good news is hear the Gospel to receive the power to do right; and we study (observe) the Word to receive the knowledge of what to do. And the God-in-us does it.