There shall be twelve stones with their names according to the names of the sons of Israel. They shall be like signets, each engraved with its name, for the twelve tribes.
The most considerable of the ornaments of the high priest was this breast-plate, a rich piece of cloth, curiously wrought with gold and purple, etc., two spans long and a span broad, so that, being doubled, it was a span square, Exo 28:16.
Commenting on Exodus 28:15-30
And thou shall make upon the breastplate chains at the ends,.... One end of them to be put to the breastplate, and the other end to the ouches on the shoulder pieces of the ephod, by which the breastplate hung from thence: the Targum of Jonathan renders it, chains of a certain determined size, of length and thickness exactly alike; or terminable ones, as it...
Exo 28:21 “And the stones shall be according to the names of the sons of Israel, twelve according to their names; seal-engraving according to each one’s name shall be for the twelve tribes.” (On אישׁ before על־שׁמו see at Gen 15:10.)