Exodus 28:11-12, 21

Engrave the names of the sons of Israel on the two stones the way a gem cutter engraves a seal. Then mount the stones in gold filigree settings and fasten them on the shoulder pieces of the ephod as memorial stones for the sons of Israel. Aaron is to bear the names on his shoulders as a memorial before the LORD.

There are to be twelve stones, one for each of the names of the sons of Israel, each engraved like a seal with the name of one of the twelve tribes.