When Moses came down from Sinai, he was carrying something that did not come from earth. Targum Pseudo-Jonathan preserves the tradition with striking specificity: God gave to Moses the two tablets of the testimony, tablets of sapphire-stone from the throne of glory, weighing forty sein, inscribed by the finger of the Lord (Exodus 31:18).
Sapphire from the throne?
This is one of the great targumic expansions. The plain Hebrew says only that the tablets were stone, inscribed by God. The targum identifies the stone as sanpirinon — sapphire, the same blue stone that Exodus 24:10 describes beneath the feet of God when the elders of Israel saw the pavement of heaven. The tablets, in this reading, were carved from the very floor of the divine throne room.
The midrashic tradition (Devarim Rabbah 3:12, c. 600 CE) extended this further. The sapphire was self-luminous — it gave off its own light, as if a piece of the divine radiance had been cut loose and handed down. The forty sein of weight (a measure of considerable heft) were so heavy that, had God not supported them, no human arm could have carried them. Moses bore them, the sages said, because the letters inscribed on them lifted themselves. When the letters fled, later in the story, the tablets became too heavy to hold.
The inscription itself was not ordinary writing. "Inscribed by the finger of the Lord" — the sages of the Talmud (Shabbat 104a, c. 500 CE) taught that the letters were cut all the way through the sapphire, readable from both sides, and that certain letters (the samekh and the final mem) hung suspended in their centers by miracle alone.
The tablets were not a document. They were an object from above, placed for a moment in human hands, with consequences we will see in the next verses.
The Maggid takes this home: sometimes God gives us a piece of heaven to carry for a while. Carry it carefully. The letters may still be flying.