How do we know the principle of preaching the gospel is true?

Scripture consistently reaffirms that the core mission of the Church is to proclaim the gospel. This is seen in the Great Commission in Matthew 28:19-20, where Jesus commands His followers to make disciples of all nations by teaching them to obey His commandments. The apostolic writings further illustrate this focus, urging the Church to be the salt and light of the world rather than to conform to worldly standards for attraction. Historical contexts of the Church also demonstrate that genuine conversions happen through a faithful proclamation of the gospel, rather than through worldly amusements or entertainments. Thus, it's evident that the truth of the gospel message lies in its power to save and transform lives when it's rightly preached.