After God had exposed a little of His beauty for Moses to see, He commanded him to come up onto Mt. Sinai again. This time, however, God required him to chisel out blank stone tablets himself (like the first ones which God had given). This was Moses' third major trip up the mountain to receive the very same law. The first time he only received spoken words. The second time he got the words and the Decalogue written on tablets which God had made. This time he received the words and God wrote on tablets which Moses had prepared.
There are many intriguing parallels between the two versions of the tablets with the two testaments. God made the first tablets completely alone... and He made the first covenant alone (with Abraham in Genesis 15:12-13). God wrote on the second set of tablets after Moses had made them... and, God made the second covenant with the faith-filled followers of Abraham through a "manmade" (well, woman-made) vessel - namely, Jesus (Galatians 4:4).
The first tablets were broken as soon as Moses got to the bottom of the mountain. And, the first covenant was broken just about as soon as it came forth (Genesis 16:2). The second set of tablets rested safely in the Ark of the Covenant and were never broken...just as the second covenant rests safely in Christ and cannot be broken (Ephesians 4:30).
And, finally, the face of Moses glowed after his second spell of forty days on the mount, which it had not done after the first forty days. This too signifies the glorious efficacy of the second covenant, a glory which the first one did not possess (Hebrews 11:13 & II Corinthians 4:4).