The Abrahamic Covenant — Genesis 15 and 17

Gen 15:5-6 records the covenant promise and Abraham's response: he "believed the LORD, and he counted it to him as righteousness." In Genesis 15 God alone passes between the pieces, binding himself by oath.

John Calvin — Institutes of the Christian Religion, and Augustine — City of God. The sign of circumcision in Gen 17:7-11 seals the promise to Abraham and his offspring.

Paul makes Genesis 15:6 the proof text of justification by faith in Rom 4:3 and Gal 3:6. The covenant with Abraham reaches forward to embrace the Gentiles in Christ.