1. justified by grace through faith (21-26)

Apostle Paul argued in 1:18-3:20 that no one on earth is righteous before God by their own effort, not even moral or religious people. All have sinned and fall short of God's glory (23). The good news (gospel) is that Jesus Christ shed his blood to atone for (take away) the sins of all who believe. Jesus' blood paid the price for our redemption. Now we are free from the power and consequences of sin. Christians are "justified," that is, righteous in God's sight. This is a free gift of God's grace, given to all believers in Christ.

2. part from works (27-31)

The Jews thought they were justified before God by obeying God's law, which included circumcision. But if their obedience and own effort made them righteous, then they could boast about it. In the gospel of Jesus no one can boast, since it's not what we've done but what Christ has done that saves us.