Although the work of redemption was not actually wrought by Christ till after His incarnation, yet the virtue, efficacy, and benefits thereof were communicated unto the elect, in all ages successively from the beginning of the world, in and by those promises, types, and sacrifices, wherein He was revealed, and signified to be the seed of the woman which should bruise the serpent’s head; and the Lamb slain from the beginning of the world; being yesterday and today the same, and forever.
Resources
The Covenant of Grace in the Old Testament by Martyn Lloyd-Jones
How Was There Salvation During the Old Testament Period? by Martyn Lloyd-Jones
The Everlasting Covenant by Martyn Lloyd-Jones
Christological Principles of Typology by by Nicholas T Batzig
The Covenant of Grace and Its Twofold Economy in the Old and New Testaments by Francis Turretin
The Covenant of Grace Identical in both Old and New Testaments by Wilhelmus a Brakel
What was the Old Testament way of salvation? by Got Questions
How Were People Saved Before Jesus Came in the Flesh? by Steve Fazekas
Redemption in the Old Testament: Biblical Studies by Dennis Whalen
Articles on Typology @Monergism
Christ in the Old Testament @Monergism
eBooks
The Old Testament Doctrine of Salvation by William Deas Kerswill
The Typology of Scripture (eBook) by Patrick Fairbairn
Gleanings in Genesis (eBook) by A. W. Pink
On the Mediator (eBook) by John Calvin
The Fountain of Life: a display of Christ in his essential and mediatorial glory (eBook) by John Flavel
Christ Set Forth (eBook) by Thomas Goodwin
The Heart of Christ in Heaven (eBook) by Thomas Goodwin
The Glory of Christ (eBook) by John Owen
The Lord of Glory (eBook) by B. B. Warfield
Spiritual Union & Communion (eBook) by A. W. Pink
The Virgin Birth by J Gresham Machen
Christ: A Complete Saviour or the Intercession of Christ and Those Who Are Privileged in It (eBook) by John Bunyan
Multimedia
The Church in the Old Testament by Jonathan Brack
Of Christ the Mediator (Ch.8, Sec.6-7) by Greg Bahnsen
Salvation in the Old Testament (MP3) by Jerusalem Chamber
How to Explain Old Testament Salvation in Christ? (YouTube) by Paul Washer
How Old Testament Saints Were Saved by D. A. Carson
How were people saved in the Old Testament? | Ligonier Conference Panel
Books
Jesus the Son of God by D A Carson
The Word Enfleshed by Oliver Crisp
What is the Incarnation by William Evans
The Son of God and New Creation by Graeme Goldsworthy
The God Who Became Human by Cole Graham
The Person of Jesus by J. Gresham Machen
The Christian’s Pocket Guide to Jesus Christ by Mark Jones
The Person of Christ by Donald MacLeod