 You should pray, and God will give them eternal life. Paul's there for a moment. Notice he says, if you see your brother or sister caught in a sin, pray for them. He's talking about you praying for your Christian brothers and sisters. This goes back, you might write this out in the side of your Bible or in your notes, Galatians 6.1. This is also what Paul taught, showing that the Scripture is harmonious all through. It doesn't contradict each other. Instead, it cooperates with each other.