Exodus 32 - 34

After Moses was 40 days and nights on the mountain of God the people grew restless, and Aaron cast a golden calf for them to worship. God is very angry with the people, and Moses intercedes with Him, so that He might not destroy them all.

God is angry with the people, but pleased with Moses, and Moses asks God to show him His glory (He wanted to see God). God hides Moses in a cave, or notch in the rock, and lets a remnant of His glory pass before him. He then declares His own Name (Yahweh), and provides definition for the meaning of His Name.

Then the LORD passed by in front of him and proclaimed, The LORD, the LORD God, compassionate and gracious, slow to anger, and abounding in lovingkindness and truth; who keeps lovingkindness for thousands, who forgives iniquity, transgression and sin; yet He will by no means leave the guilty unpunished, visiting the iniquity of fathers on the children and on the grandchildren to the third and fourth generations.
Exodus 34:6-7

This describes the very nature of God!

After another 40 days and nights Moses goes down from the mountain, and he is glowing so brightly that he has to cover his face in front of the people.