EXO 39:21

21 and coupled full strongly with the rings, which rings a lace of jacinth joined together, lest they were loosed, and slacked, and were moved (away) each from (the) other; as the Lord commanded to Moses. (And then the breastpiece was bound by its rings to the rings of the ephod, with a lace of jacinth, so that the joining would stay secure, and the breastpiece and the ephod would not separate from each other; all as the Lord commanded to Moses.)