In this connection it may also be noted that the idea of the covenant has prevented too narrow a view of the sacraments. Viewed as seals of the covenant, the sacraments possess just as universal and comprehensive significance as the covenant itself. They cease being signs of a particular grace and become what they should be: particular signs of an all-comprehensive grace. They seal Christ to us, the rich and full Christ, with all that we have in Him. We cannot limit that sealing power to any single stage of the way of salvation. Not regeneration, nor justification, nor the communion of the saints, each in itself, but all of these, as they together constitute the blessings of the covenant, are the object of sealing. If the consciousness of the covenant reflects like a mirror the glory of God, then all the separate rays come together in the sacraments, as a focal point, to one glory.
-- Italics original, bold mine, p262, Vos, Doctrine of the Covenant in Reformed Theology in Redemptive History and Biblical Interpretation