Institutes of the Christian Religion (1559) - John Calvin
Book 2 - God the Redeemer
Chapter 11 - The Difference between the Two Testaments
Sections 9-10 - Bondage of the OT and freedom of the NT
Section 9 - Paul's teaching
Romans 8:15; Heb 12:18-22; Gal 4:22-31.
"The OT struck consciences with fear and trembling, but by the benefit of the NT they are released into joy."
OT saints were still saved as we are, by faith to God's gospel promises.
But they still had to keep the ritual law, too - Gal 4:2-3.
Section 10 - Law and gospel
OT is not law, and NT gospel; the OT contains grace and mercy, too.
Children of promise in the OT lived by faith in the coming Mediator.