We are saved because we believe Jesus is the Son of God. How were people saved before Christ's birth, death, and resurrection?
This is a very insightful question. You are correct that salvation comes only through faith in Christ, according to these verses:
"Nor is there salvation in any other, for there is no other name under heaven given among men by which we must be saved" (Acts 4:12).
"I am the way, the truth, and the life. No one comes to the Father except through Me" Conn 14:6).
"For there is one God and one Mediator between God and men, the Man Christ Jesus" (1 Timothy 2:5).
These are only a few of the texts that show the exclusivity of salvation in, through, and by Jesus Christ.
A simple analogy may help explain how people were saved before Christ. If you purchased a house tomorrow by signing the papers and recording the legal documents with the proper authorities, would you be allowed to move in' before the house was fully paid, or only after? The answer, of course, is before. You are at liberty to move in based on a signed contract, even though the house has not been paid for nor has even one payment been made. Amazing! That's the power of a signature and contract law.
Well, God made a promise. He signed on the dotted line, if you will. He made a promise that is far more powerful than any man-made contract. Before time began, God promised that He would give eternal life through His Son to all those who believe (Titus 1:2). Based upon this promise of the coming Savior (Revelation 13:8; Romans 3:24, 25; Hebrews 9:15), God dealt with His people mercifully as though their debt of sin had been paid in full through the future redemptive work of Jesus. Hallelujah!
God who cannot lie nor be stopped, who opens and no one shuts and shuts and no one opens, who works and no one reverses, and who purposes and no one can annul, knew He would provide the payment for the debt of sin, and thus interacted with humanity based upon that reality. In short, God did not impute the sins of Old Testament saints against them — based on the future work of Christ (Romans 4:8).
it is critical to understand that those saints, while their understanding was limited, did have a basic understanding of the need for redemption and of the coming Savior (Hebrews 11:13, 6; a Genesis 3:15; Isaiah 53; Psalm 130:3; Job 19:25). Like New Testament saints, they are saved only through the blood of Christ. The salient point here is that God interacted with Old Testament saints based upon the following two realities: 1) His unstoppable and sure promise to send the Savior and 2) their faith in the coming Savior (even though that faith was incomplete).
The significance here — and the challenge — is to understand that salvation is by faith in Christ alone, and yet Jesus' work of redemption was, in a legal sense, applied to Old Testament saints who had faith in the living God and in His Word (John1:1,14).
We affirm, then, that Christ is the key to salvation and that faith is the key to Christ. Note the connection between Abraham's faith and righteousness (salvation): "He believed in the Lord, and He accounted it to him for righteousness" (Genesis 15:6).
Yes, there has always been only one way of salvation: namely, by faith in God as Savior! There have never been two salvific systems — one for the Jews and one for the Gentiles, or one for the Old Testament and one for the New Testament. Many people confuse the purpose and role of the old covenant as redemptive, which it is not (Galatians 2:21).
— Pastor Greg Lincoln Harrisburg, OR
From "The Bible Advocate" - Jan/Feb - 2015, a publication of the Church of God, Seventh Day, Denver, CO. USA.
IN SIMPLE TERMS: THE PEOPLE BEFORE THE BIRTH OF CHRIST LOOKED FORWARD TO THE SACRIFICE DEATH OF THE MESSIAH CHRIST JESUS; WE AFTER THE BIRTH OF CHRIST LOOK BACK TO THE MESSIAH CHRIST'S SACRIFICE OF DEATH. EITHER WAY, SINS ARE FORGIVEN THROUGH THE DEATH SACRIFICE OF THE MESSIAH JESUS. SALVATION HAS ALWAYS BEEN THE SAME FOR ANY INDIVIDUAL SINCE ADAM. ALL WHO WILL BE IN THE FIRST RESURRECTION, ALL GOD'S CHILDREN FROM THE TIME OF ADAM, WILL BE THERE BECAUSE THEIR SINS WERE WASHED AWAY IN THE BLOOD AND DEATH OF THE MESSIAH CHRIST ON THE CROSS….. ALL THEN BY GRACE THROUGH FAITH IN CHRIST JESUS, WHO IT IS WRITTEN, WAS FORE-ORDAINED TO BE THE SAVIOR OF ALL PEOPLE, BEFORE THE FOUNDATION OF THE WORLD [1 PETER 1:18-20].