Romans 6:3-5
3Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death?
4Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
5For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection:
6Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin.
Colossians 2:11-15
11In whom also ye are circumcised with the circumcision made without hands, in putting off the body of the sins of the flesh by the circumcision of Christ:
12Buried with him in baptism, wherein also ye are risen with him through the faith of the operation of God, who hath raised him from the dead.
13And you, being dead in your sins and the uncircumcision of your flesh, hath he quickened together with him, having forgiven you all trespasses;
14Blotting out the handwriting of ordinances that was against us, which was contrary to us, and took it out of the way, nailing it to his cross;
15And having spoiled principalities and powers, he made a shew of them openly, triumphing over them in it.
He is saying that we are buried with Christ in baptism, that a spiritual circumcision takes place in our hearts in baptism and we are not saved without it.