If only you had paid attention to my commands,
your peace would have been like a river,
your well-being like the waves of the sea. Isaiah 48:18
There are several instances in the Old Testament prophets where God expresses grief that his people, Israel, did not obey his commands. The above verse is one well-known example of that. This is significant for Calvinist theology in two ways. First of all, Calvinist theology implies that people do not have any decisive control over their own spiritual destinies. This implies that they also do not have control over the sins which end up damning them and that God himself determines them in some way to commit those sins. Calvinists teach unconditional reprobation or unconditional “hardening” based on a particular reading of Romans 9. The “unconditional” here means that God chooses to harden people irrespective of what they have done. We don’t know why God chooses some people to be hardened, according to Calvinists, but he does so and it is not based on their works. However, this verse clearly implies that they did have decisive control over the sins which caused their condemnation. God says, “if you had paid attention to my commandments”, which means that it was they who could choose to do so or not, to pay attention to the commandments or to not do so. It was not God who determined them one way or the other.
Second, it doesn’t make sense that God would express grief for people, many of whom would ostensibly be condemned, if he himself willed for them to become condemned. If God expresses grief for the sin that causes their condemnation, then he did not will that they be condemned. If you believe these verses along with unconditional reprobation, then you are forced to claim that God both willed that they be damned and willed that they be saved, which is a contradiction. Also, a doctrine of “two wills” doesn’t work to make sense of this contradiction, neither Biblically nor rationally.