Systematic Theology, by Louis Berkhof - New Leaven

1. ADULTS IN THE COVENANT. Adults can only enter this covenant voluntarily by faith
and confession. From this it follows that in their case, unless their confession be false,
entrance into the covenant as a legal relationship and into the covenant as a communion
of life coincide. They not merely take upon themselves the performance of certain
external duties; nor do they merely promise in addition to this, that they will exercise
saving faith in the future; but they confess that they accept the covenant with a living
faith, and that it is their desire and intention to continue in this faith. They enter upon
the full covenant life at once therefore, and this is the only way in which they can enter
the covenant. This truth is implicitly or explicitly denied by all those who connect the
confession of faith with a merely external covenant.
2. CHILDREN OF BELIEVERS IN THE COVENANT. With respect to the children of believers,
who enter the covenant by birth, the situation is, of course, somewhat different.
Experience teaches that, though by birth they enter the covenant as a legal relationship,
this does not necessarily mean that they are also at once in the covenant as a
communion of life. It does not even mean that the covenant relation will ever come to
its full realization in their lives. Yet even in their case there must be a reasonable
assurance that the covenant is not or will not remain a mere legal relationship, with
external duties and privileges, pointing to that which ought to be, but is also or will in
time become a living reality. This assurance is based on the promise of God, which is
absolutely reliable, that He will work in the hearts of the covenant youth with His
saving grace and transform them into living members of the covenant. The covenant is
more than the mere offer of salvation, more even than the offer of salvation plus the
promise to believe the gospel. It also carries with it the assurance, based on the promises
of God, who works in the children of the covenant “when, where, and how He
pleaseth,” that saving faith will be wrought in their hearts. As long as the children of the
covenant do not reveal the contrary, we shall have to proceed on the assumption that
they are in possession of the covenant life. Naturally, the course of events may prove
that this life is not yet present; it may even prove that it is never realized in their lives.
The promises of God are given to the seed of believers collectively, and not individually.
God’s promise to continue His covenant and to bring it to full realization in the children
of believers, does not mean that He will endow every last one of them with saving faith.
And if some of them continue in unbelief, we shall have to bear in mind what Paul says
in Rom. 9:6-8. They are not all Israel who are of Israel; the children of believers are not
all children of promise. Hence it is necessary to remind even children of the covenant
constantly of the necessity of regeneration and conversion. The mere fact that one is in
the covenant does not carry with it the assurance of salvation. When the children of
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