SPROUL: Baptism is a sign, and it signifies the forgiveness of sins. I don’t think that it automatically carries forgiveness of sins with it, but it’s a central sign of what our salvation is. We’re being washed with water, and the significance of that sign is cleansing, specifically cleansing from sin.
There is a dispute about the efficacy of the sacrament; namely whether it happens ex opere operato, which is simply by the exercise of the sacrament, or whether it needs to be accompanied by faith for its efficacy. I would take the latter position.
THOMAS: It’s important to emphasize that the sacraments are signs and seals to the forgiveness of sins. They are signs and seals to faith and forgiveness, but they’re not in and of themselves signs and seals that we are forgiven. They’re signs and seals of the gospel. Baptism points us to the gospel. Baptism points us to Christ, and in Him there is forgiveness of sins.