In soteriology, Tertullian does not dogmatize; he prefers to keep silence at the mystery of the cross ("De Patientia", iii). The sufferings of Christ's life as well as of the crucifixion are efficacious to redemption. In the water of baptism, which (upon a partial quotation of John 3:5) is made necessary ("De baptismo", vi.), humans are born again; the baptized does not receive the Holy Spirit in the water, but is prepared for the Holy Spirit. Humans are little fishes – after the example of the "ichthys", fish, Jesus Christ – born in water ("De baptismo", i). In discussing whether sins committed subsequent to baptism may be forgiven, Tertullian calls baptism and penance "two planks" on which the sinner may be saved from shipwreck – language which he gave to the Church ("De penitentia", xii).