This is a symbol of baptism, which now saves you-- not the putting away of the filth of the flesh, but the answer of a good conscience toward God, through the resurrection of Jesus Christ,
Peter's great Pentecostal sermon has the same meaning, where he declared that believers should repent and be baptized in order to receive the forgiveness of sins (Acts 2:38).  There is further comment on this in my Commentary on Hebrews, pp. 200-201.