Philip Melanchthon, a close associate of Martin Luther, describes how believers after Christ share the same faith as believers before Christ.
Faith in the Savior begins at the Fall
The words in Genesis [3:15]: “The Seed will crush the head of the serpent,” signify nothing other than the same thing which John says: “For this the Son of God was revealed, that he might destroy the works of the devil” [1 John 3:8].
Adam understood the promise in this way, and thereafter all the patriarchs believed that on account of this promised seed their sins were forgiven them and that they would be set free from sin and from eternal death.
Through this faith, they were righteous, not through the fulfillment of the law. By this faith, they were raised up in all dangers and terrors. Indeed they knew that this Lord was present with them, as Jacob plainly says, in Gen. 48[:16]: “The Angel who has delivered me from all harm—may he bless these boys.”; for he proclaims him Lord who had set him free from all evils, and asks of him that he would bless his descendants.
Faith in the Savior is throughout the Old Testament
These things can be understood in no other way except as pertaining to the Son of God. Paul also says that the Son of God accompanied the camp of the people of Israel [1 Cor. 10:4]. John [1:5] also says that all things were made through this Son and that the Light shines on the darkness.
All triumphs against our adversary, the devil, are imparted through this Son. Noah was preserved, Abraham defended, Joseph brought out of prison, the people freed from Egypt, and Daniel also spoke with him.
Thus the gospel of the apostles preaches Christ, and testifies that he is the sacrificial victim, liberator, and Savior, and commands us to trust this leader and liberator, as also many statements of the prophets teach, as Ps. 2[:12] says: “Kiss the Son … blessed are all who trust in him.”
Faith in the Savior is the only way to be right with God
Without this faith, i.e., trust in the mercy promised because of the Son, there is no true invocation of God, no true worship. For through this priest we have access to the Father, as we often find written.
Source: Philip Melanchthon on the Old Testament believers faith in the coming Son for the forgiveness of sins. Philip Melanchthon ( 16 February 1497 – 19 April 1560), was a German Lutheran reformer and collaborator with Martin Luther. He was the first systematic theologian of the Protestant Reformation. He was the intellectual leader of the Lutheran Reformation. He was an influential designer of educational systems. He is especially remembered and honored as the author of the Augsburg Confession, the defining document of Lutheranism within Christendom. (The Augsburg Confession was presented by the German princes to the emperor on June 25, 1530).