Targum Pseudo-Jonathan on Exodus (Exodus 24:4) describes what Moses built at dawn: Mosheh wrote the words of the Lord, and arose in the morning and builded an altar at the lower part of the mountain; and twelve pillars for the twelve tribes of Israel.
The Altar and the Twelve
One altar at the foot of Sinai. Around it, twelve standing stones. Each stone represents a tribe — Reuben, Simeon, Levi, Judah, Dan, Naphtali, Gad, Asher, Issachar, Zebulun, Joseph, Benjamin. The sons of Jacob, now a people on the brink of covenant.
The architecture is intentional. The altar is the point of contact with God. The twelve pillars are the point of contact with the people. Together they form the shape of what Israel will be — a nation where every tribe has a standing place, and where that standing always faces the same central altar.
Why Moses Writes First
Before the altar, before the stones, Moses wrote the words of the Lord. The covenant is textual before it is ritual. The laws are recorded. They will survive the pillars, survive the altar, survive the generation that witnessed them.
This is the moment the Torah becomes a written thing — Sefer HaBrit, the Book of the Covenant, mentioned in the very next verses. Israel's covenant is unique among ancient peoples because it centers on a document as much as on a shrine.
The Takeaway
When Moses built the altar, he did not build it alone. He built it inside a ring of twelve stones — a visual teaching that no Israelite encounters God individually. You approach the altar as part of a tribe, standing among other tribes, all turned toward the same center.