Written in stone
According to the Bible, God inscribed the Ten Commandments into stone: "God said to Moses, 'Come up to Me, to the mountain, and remain there. I will give you the stone tablets, the Torah and the commandment that I have written for [the people's] instruction.'" (Exodus 24:12) also referred to as "tables of testimony" (Exodus 24:12, 31:18, 32:16) or "tables of the covenant" (Deuteronomy 9 : 9, 11, 15), which he gave to Moses.
Traditional Jewish sources (Mekhilta de Rabbi Ishmael, de-ba-Hodesh 5) discusses the placement of the ten commandments on two tablets. According to Rabbi Hanina ben Gamaliel, five commandments were engraved on the first tablet and five on the other, whereas the Sages contended that ten were written on each.
While most Jewish and Christian depictions follow the first understanding, modern scholarship favours the latter, comparing it to treaty rite in the Ancient Near East, in the sense of tablets of covenant. Diplomatic treaties, such as that between Egyptian Pharaoh Ramses II and the Hittite King Hattusilis III, circa 1270 B.C.E, were duplicated on stone with a copy for each party, and the subordinate party would place their copy of the pact in the main temple to his god, in oath to the king (cf. Ezekiel 17:11-19). In a pact between a nation and its God, then, the Israelites placed both copies in their temple.
Exodus 32:15 records that the tablets "were written on both their sides". The Talmud (tractate Shabbat 104a) explains that there were miracles involved with the carving on the tablets. One was that the carving went the full thickness of the tablets.
There is a letter in the Hebrew alphabet called a samech that looks similar to the letter "O" in the English alphabet. The stone in the center part of the letter should have fallen out, as it was not connected to the rest of the tablet, but it did not; it miraculously remained in place.
Secondly, the writing was miraculously legible from both the front and the back, even though logic would dictate that something carved through and through would show the writing in mirror image on the back