Jesus died for our sins, was buried, and lives again. By joining in baptism, we’re identifying ourselves with Him.
Romans 6:4 says we have been buried with Him through baptism into death. We’re now dead to the power of sin. Being raised up out of the water expresses our new life in Christ and our union with Him.
Don't you know that all of us who were baptized into Christ 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.