1. There is no other gospel (6-7a)
The gospel is simple: Jesus died for our sins and God raised him from the dead. He did this according to God's promise in the Scripture. When we repent and believe in Jesus, we receive forgiveness of sins and eternal life. We are saved by God's grace alone, by faith alone. We need only Jesus. We do not need rituals or exciting experiences. His grace is enough to save us fully.
2. A fearsome responsibility (7b-10)
In Paul's day there were some who insisted that salvation by faith in Jesus alone was too simple. Some Jewish Christians insisted on Jesus + circumcision. In every age false prophets appear who try to 'improve' the gospel by adding or subtracting something. Paul uses strong language about those who change the gospel. We serve Jesus because we are grateful for his grace, not to earn salvation. God's servants must teach God's gospel and live before God, not before men.
Application: Lord, thank you for your saving grace.
One Word: Only Jesus