In the Priestly tradition, what is engraved upon the stone tablets that are placed in the Ark would appear to be the instructions for building the Tabernacle and all its equipment, which Moses receives from Yahweh while on Sinai (Ex 25-31).
And when he finished speaking with him in mount Sinai, he gave the two tablets of the Testimony to Moses, tablets of stone, written by the finger of God. (Ex 31:18)
I have already noted that the Bible’s various traditions have preserved two contradictory statements pertaining to who wrote the stone tablets, Moses or Yahweh (#147). Here we’re concerned with what were on these tablets.
In Exodus 24:12, attributed to the Elohist source, we are informed that Yahweh will give Moses the stone tablets which contain Yahweh’s instruction and commandment. In the redacted text as it now stands, we could easily assume that these are the very tablets that Moses then receives in Exodus 31:18, and which Moses breaks in Exodus 32:19, and which Yahweh rewrites and gives him again in Exodus 34:1. But in fact, textual critics have argued that there are two different traditions here—well actually three—each with its own ideas about what was written on these tablets.
As has already been discussed, and will be discussed further in the forthcoming contradictions, all of Exodus 25-31 and 35-40 come from the pen of P. Try reading through it as an ensemble, and then read Exodus 24 and 32-34 as another ensemble. You will immediately spot the differences in content, style, religious emphases, vocabulary, etc. Exodus 25-31 is a detailed and structured account of the instructions for the building of the Tabernacle and its equipment, and the fabrication of Aaron’s priestly garments. These are then built and made in Exodus 35-40. Read Exodus 31:18 and immediately after, Exodus 35:1—that is where the P source continues unaltered.
Although the Priestly source does not explicitly say what’s written on the stone tablets, judging from its context, it must be the actual instructions for the Tabernacle. This makes prefect sense because the cultic institution is the centerpiece of the whole priestly sacrificial ideology. And secondly because the Ten Commandments are no where mentioned in the Priestly literature! Lastly, the Priestly text has these tablets deposited in the Ark which seats in the Holy of Holies—the inner shrine of the Tabernacle, only accessible to the Aaronid priest.
Furthermore, Exodus 34:1 presents its own set of problems vis-à-vis the content of these tablets. It states that Yahweh wrote on these second pair of tablets exactly what was written on the first pair. But this is indeed not the case at all (see #135). There are in fact two different, and once independent, traditions of the Ten Commandments (#134).
Critiques have therefore surmised that the Elohist’s tablets (Ex 24:12) contained some form of the Ten Commandments and/or the laws. The Yahwist’s tablets (Ex 34:27-28) contain only the Ten Commandments, but they are a different Ten Commandments (Ex 34:14-26). And the Priestly version seemed to have contained the instructions for building the Tabernacle.
Furthermore, the narrative that we now have in the redacted text—the giving, breaking, and regiving of the tablets—is seen as the work of the redactor who stitched these traditions together.