A scripture on what baptism signifies:
Or don’t you know that all of us who were baptized into Christ Jesus were baptized into his death? We were therefore buried with him through baptism into death in order that, just as Christ was raised from the dead through the glory of the Father, we too may live a new life. (Romans 6:3-4)
From Article 11 of the Confession of Faith from a Mennonite Perspective:
We believe that baptism by water is a sign that a person has repented, received forgiveness, renounced evil, and died to sin, through the grace of God in Christ Jesus.