Exodus 28:21
And the stones shall be with the names of the children of Israel, twelve, according to their names, like the engravings of a signet; every one with his name shall they be according to the twelve tribes.
Cross-references
Exodus 28:9-11 describes engraving the names on onyx stones for the ephod — identical practice for the breastplate here.
Exodus 28:11 describes engraving the tribes' names on two onyx shoulder stones — similar signet engraving for the same purpose of representing the twelve tribes.
Exodus 24:4 describes twelve pillars for the twelve tribes — another instance of each tribe represented by a physical object, like the breastplate stones.
Exodus 39:10 records the actual setting of stones in the breastplate, fulfilling the instruction given in Exodus 28:21 — a parallel account of the same breastplate.
In Revelation 21:12, the New Jerusalem's gates are inscribed with the twelve tribes' names, echoing the tribal stones on the high priest's breastplate.
Matthew 19:28 promises the disciples will judge the twelve tribes of Israel — referencing the same twelve tribes as those on the breastplate stones.
Genesis 49:28 concludes Jacob's blessings, naming the twelve tribes of Israel — the same tribes whose names are engraved on the breastplate stones.
Joshua 4:9 sets up twelve memorial stones for the tribes of Israel — another use of twelve stones to represent the twelve tribes.
1 Kings 18:31 uses twelve stones for an altar, representing the twelve tribes — same symbolic use of stones for the tribes.