John Newton and John Owen were two very different Christians but they were united in their view of how Old Testament believers were saved and what their faith was in.
John Newton taught that the Gospel of Jesus Christ was revealed immediately after Adam and Eve’s first sin and became the object of faith from that moment on.
The Lord Jesus was promised under the character of the seed of the woman, as the great deliverer who should repair the breach of sin, and retrieve the ruin of human nature. From that hour, he became the object of faith, and the author of salvation, to every soul that aspired to communion with God, and earnestly sought deliverance from guilt and wrath (Works, Vol. 3, p. 3).
Newton went on to say that although this revelation of Christ was initially veiled under types and shadows, “it was always sufficient to sustain the hopes, and to purify the hearts, of the true worshippers of God.” Newton even goes so far as to say that they were Christians.
That the patriarchs and prophets of old were in this sense Christians, that is to say, that their joy and trust centered in the promised Messiah, and that the faith, whereby they overcame the world, was the same faith in the same Lord with ours, is unanswerably proved by St. Paul in several passages; particularly in Heb. xi. where he at large insists on the characters of Abel, Enoch, Noah, Abraham, and Moses, to illustrate this very point.
What about when the law came at Sinai? Did that change or annul the Gospel promises? No, says Newton.
His grace always preserved a spiritual people amongst them, whose faith in the Messiah taught them the true meaning of the Levitical law, and inspired them with zeal and sincerity in the service of God.
John Owen puts it even stronger.
That the faith of all believers, from the foundation of the world, had a respect unto [Christ], I shall afterwards demonstrate; and to deny it, is to renounce both the Old Testament and the New. (John Owen, Works, Vol. 1, p. 100).
Owen, however goes on to argue that their faith was different to ours in this respect, that “this faith of theirs did principally respect his person” but they little understood “his office, or the way whereby he would redeem the church.”
He gives Peter as an example of this distinction in Matthew 16:16 where he confesses faith in Christ’s person but then almost immediately rejects the idea that he would save by suffering and dying (v. 22).
Owen accepts that the Old Testament, especially the sacrificing work of the priests, revealed Christ’s office and work also, but much of that was in shadow form, especially when contrasted with the “glorious revelations they had of his person” so that “their faith in him was the life of all their obedience.”
In answer to those who wonder what’s the point of reading the Old Testament, Owen argues that with the benefit of New Testament light, “The meanest believer may now find out more of the work of Christ in the types of the Old Testament, than any prophets or wise men could have done of old.”
Despite this disadvantage that Old Testament believers labored under, Owen vehemently refutes the idea that there was ever any way of salvation for anyone apart from faith in Christ.
From the giving of that promise the faith of the whole church was fixed on him whom God would send in our nature, to redeem and save them. Other way of acceptance with him there was none provided, none declared, but only by faith in this promise.
After a survey of Old Testament believers to prove his point, Owen returns to clarify his basic person/work distinction.
It is true that both these and other prophets had revelations concerning his sufferings also. For “the Spirit of Christ that was in them testified beforehand of his sufferings, and the glory that should follow,” (1 Pet. 1:11)….Nevertheless their conceptions concerning them were dark and obscure. It was his person that their faith principally regarded. Thence were they filled with desires and expectations of his coming, or his exhibition and appearance in the flesh. With the renewed promises hereof did God continually refresh the church in its strait and difficulties. And hereby did God call off the body of the people from trust in themselves, or boasting in their present privileges, which they were exceedingly prone unto.