5. If infants were once members, and the Church remains the same, then they are still members, unless some positive divine enactment excluding them can be found.
It was a positive divine enactment which brought them in and gave them a place in the Church. Unless we can find a positive divine enactment casting them out of the church into which they were placed under the Old Testament administration of the covenant of grace, then we are not only justified in assuming that they still have a place, but we err greatly in assuming that they don't. I challenge anyone to produce such an act of repeal and exclusion. We have already demonstrated the identity of the church under both administrations. Scripture clearly teaches the perpetuity of the Abrahamic covenant. In this covenant, not merely the lineal descendants of Abraham, but all the nations of the earth were to be blessed. We do not find even the slightest hint in the New Testament that this high privilege granted to the infant children of believers is, or ever was withdrawn.
Opponents of infant baptism nearly always resort to an appeal about the lack of a New Testament warrant for the practice. The advocates of infant baptism are under no obligation to produce an express warrant in the New Testament for the membership of the children of believers. That warrant was given in the most formal and express terms possible 2,000 years before the New Testament was written. It has never been revoked and therefore firmly remains and is indisputably still in force.
It is truly lamentable that our Baptist brothers cannot be prevailed upon to see the length and breadth of this fact. There were little babies, 8 days old, fully and publicly acknowledged as members of the covenant community - a community consecrated to God - and stamped with a covenant seal by which they were formally bound as the seed of believers to be entirely and forever the Lord's. I don't see how infant baptism and infant membership in the church can be ridiculed without impugning the wisdom of God who was with “his church in the wilderness, and whose ways are all wise and righteous” (Acts 7:38).
There are two mistakes that are likely to be made regarding members of the covenant under the Old Testament administration of the Covenant of Grace:
1. Presume all were saved
2. Presume most weren't
As I never tire of saying: Covenant is not co-extensive with election. But, God is faithful to His covenant promise to be a God to us and our offspring. None of the Old Testament narrative books appear to work on the assumption that that the sins of Israel's and Judah's kings was to be simply expected because they were unregenerate. It is always, always cast in the language of unfaithfulness to God. The cases of reprobation in the covenant community are not there to undermine our trust in God's promise to be ours and our children's God.
Mistake #1 equates covenant with election. Scripture flatly repudiates this. Mistake #2 emphasizes the cases of reprobation (Cain, Esau, etc.) to the detriment of God's promise. We therefore admit that covenant is not co-extensive with election, nevertheless, we do not let this fact become so big in our eyes as to undermine our confidence in God's covenant promise.