And the LORD said to Moses, "Write these words, for in accordance with these words I have made a covenant with you and with Israel." So he was there with the LORD forty days and forty nights. He neither ate bread nor drank water. And he wrote on the tablets the words of the covenant, the Ten Commandments. When Moses came down from Mount Sinai, with the two tablets of the testimony in his hand as he came down from the mountain, Moses did not know that the skin of his face shone because he had been talking with God. Aaron and all the people of Israel saw Moses, and behold, the skin of his face shone, and they were afraid to come near him. But Moses called to them, and Aaron and all the leaders of the congregation returned to him, and Moses talked with them. Afterward all the people of Israel came near, and he commanded them all that the LORD had spoken with him in Mount Sinai. And when Moses had finished speaking with them, he put a veil over his face. Whenever Moses went in before the LORD to speak with him, he would remove the veil, until he came out. And when he came out and told the people of Israel what he was commanded, the people of Israel would see the face of Moses, that the skin of Moses' face was shining. And Moses would put the veil over his face again, until he went in to speak with him.
Exodus 34:27-35
This is the passage which forms the basis of Paul's exposition in 2 Corinthians 3:12-18 of the contrast between the old and the new covenants. This is made more difficult for us by the AV rendering of 33, which reads 'till Moses had done speaking with them', and thereby exactly reverses the meaning of the original which has 'when Moses had done speaking with them'. What is being said is this: As Moses came down from the mount from his holy converse with God, the skin of his face shone, reflecting the radiance of the divine glory that he had been privileged to behold (34: 5ff). This was so evident and awesome that Aaron and the people were afraid to approach him (30). Moses delivered the Lord's commands to the people (32), and when he had done speaking with them (i.e. when his official intercourse with them was finished) he veiled his face (33). This means that whenever he spoke for God he unveiled his face, but at other times he wore the veil except when he went into the presence of the Lord and spoke with Him. In 2 Corinthians 3, Paul says that Moses thus veiled his face so that the Israelites 'might not see the end of the fading splendour' (RSV), i.e. lest they should see the glory fading and - presumably - consider the law which Moses was giving them to be of only passing importance and significance. The point Paul makes is that the use of the veil was a symbol of the fact that Israel did not see that the old covenant was transitory, and that its glory was to be lost in that of the new. But the simplest and most obvious lesson here is that the 'shining' is a symbol of the moral glory and transformation that can be seen in the face and life of those who are touched by His grace.