Wherefore the Apostle says
(Gal. 3:23): "Before the faith came, we were kept under the law shut
up (_conclusi_), unto that faith which was to be revealed." Now it is
evident that the same thing it is, which gives a disposition to the
end, and which brings to the end; and when I say "the same," I mean
that it does so either by itself or through its subjects. For the
devil would not make a law whereby men would be led to Christ, Who
was to cast him out, according to Matt. 12:26: "If Satan cast out
Satan, his kingdom is divided" [Vulg.: 'he is divided against
himself']. Therefore the Old Law was given by the same God, from Whom
came salvation to man, through the grace of Christ.

Reply Obj. 1: Nothing prevents a thing being not perfect simply, and
yet perfect in respect of time: thus a boy is said to be perfect, not
simply, but with regard to the condition of time. So, too, precepts
that are given to children are perfect in comparison with the
condition of those to whom they are given, although they are not
perfect simply. Hence the Apostle says (Gal. 3:24): "The law was our
pedagogue in Christ."

Reply Obj. 2: Those works of God endure for ever which God so made
that they would endure for ever; and these are His perfect works. But
the Old Law was set aside when there came the perfection of grace;
not as though it were evil, but as being weak and useless for this
time; because, as the Apostle goes on to say, "the law brought
nothing to perfection": hence he says (Gal. 3:25): "After the faith
is come, we are no longer under a pedagogue."

Reply Obj. 3: As stated above (Q. 79, A. 4), God sometimes permits
certain ones to fall into sin, that they may thereby be humbled. So
also did He wish to give such a law as men by their own forces could
not fulfill, so that, while presuming on their own powers, they might
find themselves to be sinners, and being humbled might have recourse
to the help of grace.

Reply Obj. 4: Although the Old Law did not suffice to save man, yet
another help from God besides the Law was available for man, viz.
faith in the Mediator, by which the fathers of old were justified
even as we were. Accordingly God did not fail man by giving him
insufficient aids to salvation.
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THIRD ARTICLE [I-II, Q. 98, Art. 3]

Whether the Old Law Was Given Through the Angels?

Objection 1: It seems that the Old Law was not given through the
angels, but immediately by God. For an angel means