In explaining the relationship between the sign and the seal in the sacraments Calvin shows the similarity between the sacramental offer to unbelievers and the free offer of the gospel to unbelievers:

They are not reasoning closely enough when they argue that the sacraments are not testimonies of God’s grace because they are also offered to the wicked, who, however, do not find God more favorable but rather incur a heavier condemnation.  For by the same argument, because the gospel is heard but rejected by many, and because Christ was seen and recognized by many but very few of them accepted him, neither gospel nor Christ would be a testimony of God’s grace […] It is therefore certain that the Lord offers us mercy and the pledge of his grace both in his Sacred Word and in his sacraments.  But it is understood only by those who take Word and sacraments with sure faith, just as Christ is offered and held forth by the Father to all unto salvation. (Institutes, IV.14.7.)