The righteous shall live by his faith
The doctrine of justification by faith is sometimes thought to first appear in the New Testament as part of the New Covenant – a totally new divine means of salvation. It is through faith that we live and are made righteous.
It is easily misunderstood as only a NT teaching because it does appear often in the NT: Romans 1:17, Galatians 3:11, and Hebrews 10:38. One could mistakenly assume salvation in the OT is by the law, through works and salvation in the NT is by grace, through faith. Actually, however, when the NT writers penned these words, they were quoting the OT book of Habakkuk!
Salvation in the OT is the same as in the NT! The life and righteousness of Christ are applied to the believer through the means of faith! We believe on Christ, and because of His life, death, and resurrection on our behalf, we then are credited with His righteousness and awarded eternal life in Him! OT believers were looking ahead to the promise in faith. We look back on the promised fulfilled in faith.
The righteous shall live by his faith!