How do we know the stability of the gospel is true?

The truth of the gospel's stability is affirmed in Galatians 1:6-9, where Paul expresses astonishment that some have turned to a different gospel. He emphasizes that even if an angel from heaven were to preach another gospel, he should be accursed. This underscores that the gospel is immutable; it is not subject to change or reinterpretation. The gospel's nature is that it remains constant, providing a reliable anchor for believers in contrast to the vacillating nature of humanity and false teachings.