God wrote the Law He had given to Moses onto stone tablets.
Once GOD finished instructing Moses upon Mount Sinai, GOD gave Moses two stone tablets containing the Law.
18 So when He made an end of speaking with Moses on Mount Sinai, He gave him two tablets of testimony, tablets of stone, written with the finger of God.
(Exodus 30:11-16 OSB)
This first set of tablets did not last long.