Deuteronomy 27-30

In Deut 29:29 Moses makes a very interesting statement about God's nature. "Secret things belong to the LORD" so it should never surprise us that there are mysteries which we will never witness and others that we see but never understand. We could quit at that point and live in marvel of God's fantastic nature. But Moses doesn't stop. He continues by pointing our that the King of mysteries has revealed some things to Israel. And those revelations were for a bigger purpose than the people might suspect. The greatness of God's mysteries were revealed so that all believers, ancient Israel in the context and modern believers who read the same words, would believe in God and obey him.
The idea Moses present seems to have been copied by the apostle John who closed his resurrection story with a similar explanation of Jesus' works of wonder (John 20:30-31).
Stuart