Why did Paul emphasize the gospel not being from man?

Paul emphasized that the gospel he preached was not from man but received directly from the revelation of Jesus Christ (Galatians 1:11-12) to assert its divine authority and authenticity. He was confronting false teachings that suggested adherence to human traditions and works were essential for salvation, rather than faith in Christ alone. By affirming the gospel's divine origin, Paul underscored that salvation is a sovereign act of God, not a product of human invention or effort. This distinction serves to protect the purity of the gospel and encourages believers to trust in the sufficiency of Christ's finished work alone for salvation.