Through God’s dealings with Abraham, we see that the success of the covenant of grace depends finally on the work of our Creator alone. For example, we know that the Lord did not bless Abraham and Sarah with children until they were quite old (Gen. 21:1-7). God had to intervene miraculously to overcome their barrenness. He alone brought the promise to pass, showing us that Abraham had to rely fully on God for the covenant to succeed. In giving Abraham and Sarah a son when they were well past their childbearing years, the Lord provided tangible evidence of the sufficiency of His grace and confirmed what He had revealed years earlier in regard to His bringing His promises to pass. We find this revelation in Genesis 15, which records Abram’s faith in God’s promise to give him an heir. Abram was justified by the faith that trusted in the Lord’s promises alone (vv. 1-6). However, this does not mean that His faith, though ever present, was always strong. Almost immediately after believing the Lord’s promise to give him a son through Sarah, the patriarch’s trust began to waver, and he asked God for a sign that He would keep His promise (vv. 7-8). Remarkably, the Lord did not condemn Abram for His doubt; rather, He graciously condescended to Abram’s weakness by showing His faithfulness in a manner that the patriarch would easily understand. When covenants were made between two parties in the ancient Near East, the parties to the covenant often cut up animals and laid them side by side so that there was a path created between the animal parts. As the covenant was made, these parties would walk between the animals, calling upon themselves a curse if they did not meet their covenant obligations. Basically, they were asking for the same destruction that the animals endured to fall upon them if they broke the pact. What makes the covenant with Abram so incredible is that only one person walks between the pieces—God Himself, in the form of a smoking pot and flaming torch (vv. 9-16). God alone vows to receive the covenant curse if He does not keep His promise to Abram. This is a sign that the Lord cannot and will not fail, for if He did, He would be changed or destroyed—which is impossible. By this act, God showed that the covenant would achieve its purposes no matter what. Our obedience is not unimportant, but we are sinners and fail regularly, so the Lord alone can keep the covenant perfectly. He does the work—through Christ—to reckon us obedient to the covenant of works that we broke, and He does it entirely by grace.