Meaning: An unalterable tradition.
Exodus 31:18 And he gave unto Moses, when he had made an end of communing with him upon mount Sinai, two tables of testimony, tables of stone, written with the finger of God.
Deut. 9:10 And the LORD delivered unto me two tables of stone written with the finger of God; and on them was written according to all the words, which the LORD spake with you in the mount out of the midst of the fire in the day of the assembly.