Catechism of the Catholic Church §1964 — excerpt
The Old Law is a preparation for the Gospel. "The Law is a pedagogy and a prophecy of things to come." It prophesies and presages the work of liberation from sin which will be fulfilled in Christ: it provides the New Testament with images, "types," and symbols for expressing the life according to the Spirit.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: St. Irenaeus, Adv. haeres. 4, 15, 1: PG 7/1, 1012 · St. Thomas Aquinas, STh I-II, 107, 1 ad 2