15 The principal purpose to which the plan of the old covenant was directed was to prepare for the coming of Christ, the redeemer of all and of the messianic kingdom, to announce this coming by prophecy (see Luke 24:44; John 5:39; 1 Peter 1:10), and to indicate its meaning through various types (see 1 Cor. 10:12). Now the books of the Old Testament, in accordance with the state of mankind before the time of salvation established by Christ, reveal to all men the knowledge of God and of man and the ways in which God, just and merciful, deals with men. These books, though they also contain some things which are incomplete and temporary, nevertheless show us true divine pedagogy. These same books, then, give expression to a lively sense of God, contain a store of sublime teachings about God, sound wisdom about human life, and a wonderful treasury of prayers, and in them the mystery of our salvation is present in a hidden way. Christians should receive them with reverence.
Source: Dei Verbum (Vatican.va)