"NOW to Abraham and his seed were the promises made. He saith not, And
to seeds, as of many; but as of one. And to thy seed, which is Christ. And this I
say, that the covenant, that was confirmed before of God in Christ, the law, which
was four hundred and thirty years after, can not disannul, that it should make the
promise of none effect."
God's covenant with Abraham was not a covenant of law, but of promise: not
of works, but of faith. This covenant, as we have seen, and as is even here said,
was not only confirmed, but was even doubly confirmed, "in Christ," at the time of
the making of the covenant. Then, since the covenant, even though a man's,
once confirmed, can not be disannulled, neither can anything be added to it, it is
perfectly plain that the law, which entered four hundred and thirty years
afterward, was never intended to change the character of the covenant. The law
did not enter in any sense to take the place of the promise. In the entering of the
law there was never any purpose in the mind of God that the works of the law
should take the place of righteousness by faith.
But just here was the great mistake that was made by Israel: they utterly
mistook their own standing, and the meaning of what the Lord gave to them, and
his purpose in the giving of all that came after that covenant was confirmed. If the
covenant with Abraham had been held in faithfulness, nothing else would have
ever been needed to enter. But, when the real truth and virtue of that covenant
were not discerned, and men went further into unbelief and darkness, the Lord
followed them, and employed means and gave instruction to bring them from
unbelief and darkness to the faith, light, and blessing of the covenant that he had
made.
For, "if man had kept the law of God, as given to Adam after his fall,
preserved by Noah, and observed by Abraham, there would have been no
necessity for the ordinance of circumcision. And if the descendants of Abraham
had kept the covenant of which circumcision was a sign, they would never have
been seduced into idolatry, nor would it have been necessary for them to suffer a
life of bondage in Egypt. They would have kept God's law in mind, and there
would have been no necessity for it to be proclaimed from Sinai, or engraved
upon the tables of stone. And had the people practiced the principles of the ten
commandments, there would have been no need of the additional directions
given to Moses.
"The sacrificial system, committed to Adam, was also perverted
by his descendants. Superstition, idolatry, cruelty, and
licentiousness corrupted the simple and significant service that God
had appointed. Through long intercourse with idolaters, the people
of Israel had mingled many heathen customs with their worship;
therefore the Lord gave them at Sinai definite instruction
concerning the sacrificial service."–"Patriarchs and Prophets," page
364.
The law entered in written form, ordinances were established, and all only
because of their unbelief and transgression. None of these things were ever
necessary to the covenant, nor were they parts of the covenant: the covenant 
was complete in itself when it was confirmed, and being confirmed, nothing could
possibly be added to it.
Therefore nothing that ever came afterward was essential to the covenant.
But because of their unbelief and transgression, these things were essential to
them, to help them to the place where they could discern the truth, the light, and
the purpose of the covenant; and where in faith they could enjoy all its blessings
and its power. In other words, these things were all to help them to an
enlightened faith–the true faith of the covenant–the faith of Christ. Accordingly, in
another place, it is written: "The law entered that the offense might abound [to
make sin appear "that sin by the commandment might become exceeding
sinful"]. But, where sin abounded grace did much more abound, that, as sin hath
reigned unto death, even so might grace reign through righteousness unto
eternal life, by Jesus Christ our Lord." Thus the object of the entering of the law
was to bring men to Jesus Christ. And the object of all that came in after the
covenant was made and confirmed was to help them to a true knowledge of that
covenant.
But instead of receiving all these things in this light, and using them for this
purpose,–the purpose only of coming to the full faith of the covenant of
Abraham,–Israel made the mistake of putting all these things in the place of the
covenant, and using these, instead of God's covenant, as the way of salvation.
Thus the law of God which, as we have seen, entered to give the knowledge of
sin, and so impress the need of the Saviour provided in the covenant with
Abraham, Israel turned into the way of salvation by their own endeavors to do the
law.
The law of the Levitical priesthood, which was instituted to instruct them with
respect to the true,–the Melchisedec, priesthood of the covenant with Abraham,–
Israel turned from this purpose, and made it the final priesthood, and expected
salvation and perfection by it. Heb. 7:11.
The earthly sanctuary and its services, which were given in connection with
the Levitical priesthood, and which were given to instruct them concerning the
true,–the heavenly sanctuary and its services, in which Christ was to be priest
after the order of Melchisedec,–this Israel also perverted, and made it the final
service, and expected salvation by this service. Ps. 110:4; Heb. 6:13-20; 7:9-22,
28; 8:1-5; 9:2-28; 10:1-17.