William,

You do appreciate that the one covenant of grace is established with Christ, the single Seed of Abraham. In him the covenant is established with the elect as well. The reason we baptize the children of professing believers is because although the covenant with Abraham was established with Christ and the elect in him, God commanded Abraham to administer the covenant with his household. Since God never abrogated this principle, we dare not stop. The covenant is made with the invisible church, but we are to administer it to professors and their offspring.

Blessings,

Ron