That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. (Romans 10:9)
Belief in your heart comes before confession with your mouth. What you believe in your heart, you must confess with your mouth. The gospel is gospel not when it is believed but when it is confessed.
The rock on which Jesus built the church is not Peter’s confession but a confessing Peter.
Christian faith is not a private deal you make with God. It is a public confession. Christianity is both a belief and a confession. It is not enough that God knows you’re a Christian. Others must know it too.