God always planned for our justification by faith. As for all who lived faithfully before Christ's human life, death, and resurrection, it is applied retroactively (Romans 4). Since God knew Adam and Eve would misuse the freedom of choice He gave them, leading to sin, He made provision for their justification (and ours) through the blood of Jesus Christ before the foundation of the world (Hebrews 9:26; I Peter 3:19-21; Revelation 13:8).