Works and Grace
Ephesians 2:4 But God, who is rich in mercy, because of His great love with which He loved us,
Ephesians 2:5 even when we were dead in trespasses, made us alive together with Christ (by grace you have been saved),
Ephesians 2:6 and raised us up together, and made us sit together in the heavenly places in Christ Jesus,
Ephesians 2:7 that in the ages to come He might show the exceeding riches of His grace in His kindness toward us in Christ Jesus.
Ephesians 2:8 For by grace you have been saved through faith, and that not of yourselves; it is the gift of God,
Ephesians 2:9 not of works, lest anyone should boast.
Ephesians 2:10 For we are His workmanship, created in Christ Jesus for good works, which God prepared beforehand that we should walk in them.
Romans 3:20 Therefore by the deeds of the law no flesh will be justified in His sight, for by the law is the knowledge of sin.
Paul is wrapping up what he has been harping on the Jews and subsequently anyone that wants to boast because they keep the law and think that it makes them righteous. In fact it defines them as sinners as we saw in the previous verse and Paul expounds a little more here