וְעָשִׂ֧יתָ עַל־הַחֹ֛שֶׁן שַֽׁרְשֹׁ֥ת גַּבְלֻ֖ת מַעֲשֵׂ֣ה עֲבֹ֑ת זָהָ֖ב טָהֽוֹר׃
And thou shalt make upon the breastplate plaited chains of wreathen work of pure gold.
Read kabbalistic (mystical) interpretation of Exodus 28:22: and classical mystical sources.