"To believe the gospel" means accepting and having faith in the message or teachings of the gospel, which is the good news about Jesus Christ and his salvation.
Sentences with «to believe the gospel»
It is no wonder that I first believed the gospel there. (religion-online.org)
he that does not believe the gospel of Jesus will not line up to the word of God and they sure wont be baptized. (redeeminggod.com)
«I would not believe the Gospel unless moved thereto by the authority of the Church.» (religion.blogs.cnn.com)