Typology is the study of how persons, events, and institutions in the Old Testament served as divinely ordained patterns that prefigured the work and person of Jesus Christ. While all Reformed traditions affirm the reality of these shadows, there is debate regarding how they function within the Covenant of Grace, with some traditions emphasizing continuity in signs and others emphasizing the distinction between the type and the substance found only in Christ.
In the Reformed tradition, a type is an exhibition of things expected, providing an imitative anticipation of the future. As noted in On the Holy Spirit Ch. 14 §31, the history of Israel and its ordinances—such as the exodus or the paschal lamb—were recorded to show forth the salvation later accomplished by Christ. These are not merely human inventions but are divinely intended shadows that point toward the reality of the gospel. As the Belgic Confession Art. 25 states, while the ceremonial shadows have ceased at the coming of Christ, their substance remains with us in Jesus, in whom they have their completion.
The danger in studying typology is to judge the reality by the shadow. We must remember that the types of the Old Testament were sufficient to build up the elect in faith in the promised Messiah, as noted in the Westminster Larger Catechism Q.34, yet they were always pointing away from themselves toward the Mediator. As On the Holy Spirit Ch. 14 §32 warns, comparing the typified reality with the type can sometimes lead people to disparage the gospel, failing to see that while the types were dreams or shadows, Christ is the substantial existence. We are reminded that we are more sinful than we dared believe, needing such grace, yet more loved in Christ than we dared hope, as He is the One to whom all the prophets bore witness.