Exodus 34:28 And he was there with the Lord forty days and forty nights; he did neither eat bread, nor drink water. And he wrote upon the tables the words of the covenant, the Ten Commandments.
For the second time Moses was in the glory of God’s presence to write the Words of the Covenant (the Ten Commandments). He had broken the first tablets in the golden calf incident. The Lord is showing Moses, and us, how serious and solemn His Covenant is, and how important these Ten Commandments are. By the way, Jesus repeats, explains, and details the practical meaning of the Commandments in the Sermon on the Mount.
In both instances, the keeping of the Law is presented as the response to the Gospel of grace and salvation. The Gospel gives the desire, motivation and the power to keep the Law. When we fail, provisions are made to repent of sin, return to the Lord, and receive forgiveness.
We must not underestimate the serious nature of the Law and its consequences. Moses didn’t. He fasted for forty days and forty nights, neither eating nor drinking. This was a supernatural fast, for a human being can survive, even thrive, not eating for forty days, but he cannot survive not drinking for more than three days. This miracle is a sign of Moses’ inward faith response to God’s Covenant.
Fasting is a response, like prayer; it is not a manipulation of God, like a sacrifice, to show Him serious we are so He answers our prayer. Luther: “Fasting is indeed fine outward training,…but faith in the words.” Moses’ fasting was a faith response to an awesome event of an awesome God. Prayer and fasting can be for us a proper response to the awesome Christ Event.