Romans 6:4

Romans 6:4. Therefore 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 as we also should walk in newness of life.

There is a parallel between Christ and the true Christian. There is a likeness between the Head of the Church and the members of his mystical body. Christ died, and was buried, and his people are reckoned as dead and buried in him.