In the first two books of sacred scripture we find two promises given by God. One was to Abraham which promised that a nation will rise from him, and his descendants will be as numerous as the stars. The other is the covenant given to Moses on Mount Sinai. In these two stories we have two things at work. In the Abraham promise we have a story of faith, and in the covenant we have something that is conditional. As Collins puts it “The blessings of the covenant are contingent on the observance of the law (Collins, page 121 ).”
In Exodus 12:2 we read “I will make of you a great nation, and I will bless you, and make you name great, so that you will be a blessing.” Abraham had two choices at this point. He could tell God that He was crazy and move on with his life, or He could accept this promise by faith. The book of Hebrews tells us that he accepted by faith and it was credited to him as righteousness (Hebrews 11:8-16). This was a promise that was never to be lost.
In contrast to that we have the covenant. The lord told the Moses that He heard the cries of the people. He would be their God, and they will be his people. It was a mutual relationship of sorts. The Lord would do what He said and the Israelites must do the same. We see in the story of the Golden calf that this was not the case. The people rebelled and created a Golden calf and worshipped it as there god. This was in direct violation of the first and second commandments. And according to the book of the covenant the penalty was death and many were slaughtered by the Levites (Exodus 2:28). Though they broke the covenant Moses sought to reconcile on behalf of the people. The Lord forgave the Israelites and reinstated the covenant showing how merciful and just He truly is.
Both stories are about God and show that He is true to His promises. However one was to a holy man that sought to do the will of god in everything he did. The other was a young nation who was trying to figure out exactly who they were.
Collins, John J. Introduction to the Hebrew Bible. Minneapolis: Fortress, 2004.