being that the precepts of the natural law were
insufficient to make man live aright, and it became necessary to have
a written code of fixed laws, and together with these certain
sacraments of faith. For it was necessary, as time went on, that the
knowledge of faith should be more and more unfolded, since, as
Gregory says (Hom. vi in Ezech.): "With the advance of time there was
an advance in the knowledge of Divine things." Consequently in the
old Law there was also a need for certain fixed sacraments
significative of man's faith in the future coming of Christ: which
sacraments are compared to those that preceded the Law, as something
determinate to that which is indeterminate: inasmuch as before the
Law it was not laid down precisely of what sacraments men were to
make use: whereas this was prescribed by the Law; and this was
necessary both on account of the overclouding of the natural law, and
for the clearer signification of faith.

Reply Obj. 3: The sacrament of Melchisedech which preceded the Law is
more like the Sacrament of the New Law in its matter: in so far as
"he offered bread and wine" (Gen. 14:18), just as bread and wine are
offered in the sacrifice of the New Testament. Nevertheless the
sacraments of the Mosaic Law are more like the thing signified by the
sacrament, i.e. the Passion of Christ: as clearly appears in the
Paschal Lamb and such like. The reason of this was lest, if the
sacraments retained the same appearance, it might seem to be the
continuation of one and the same sacrament, where there was no
interruption of time.
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FOURTH ARTICLE [III, Q. 61, Art. 4]

Whether There Was Need for Any Sacraments After Christ Came?

Objection 1: It seems that there was no need for any sacraments after
Christ came. For the figure should cease with the advent of the
truth. But "grace and truth came by Jesus Christ" (John 1:17). Since,
therefore, the sacraments are signs or figures of the truth, it seems
that there was no need for any sacraments after Christ's Passion.

Obj. 2: Further, the sacraments consist in certain elements, as
stated above (Q. 60, A. 4). But the Apostle says (Gal. 4:3, 4) that
"when we were children we were serving under the elements of the
world": but that now "when the fulness of time" has "come," we are no
longer children. Therefore it seems that we should not serve God
under the elements of this world, by making use of corporeal
sacraments.

Obj. 3: Furt