For this is a word of promise, “At the appointed time I will come, and Sarah will have a son.” Not only so, but Rebecca also conceived by one, by our father Isaac. For being not yet born, neither having done anything good or bad, that the purpose of God according to election might stand, not of works, but of him who calls, it was said to her, “The elder will serve the younger.”
It is very difficult for us, as fallen humans, to accept the fact that God would give His gifts simply because He chose to do it. We tend to think that we need to do something to earn God’s favor and His free gifts. It just doesn’t make any sense for us to try to earn a free gift. In fact, God can’t give a free gift if we start paying for it.
Abraham and Sarah tried to work out God’s plan for them by having a son through one of their servants but that wasn’t what God had in mind. Their involvement is not what God wanted. What He did, He did on His own and according to His own will.
The same goes for Isaac’s children. Isaac’s wife, Rebecca, was told by God that the Jacob would end up being the leader and be blessed by God instead of his older brother. Again, God’s promise was made before any man could involve himself in the outcome. When God gives something, it must not be spoiled by a transaction. We can’t earn the free gifts of God and it is wrong for us to attempt to pay for them in any way. We can offer our thanks and we can freely give to God and others, but we should not attempt to re-pay or pay God back. We get what we get from God, not because we are so good, but simply because He chose us. Because of this, God deserves all of the glory for what we have been given.