Then they tied the rings of the breastpiece to the rings of the ephod with a cord of blue yarn, so that the breastpiece was above the waistband of the ephod and would not swing out from the ephod, just as the LORD had commanded Moses.

Exodus 25:7
and onyx stones and gemstones to be mounted on the ephod and breastpiece.

Exodus 28:8
And the skillfully woven waistband of the ephod must be of one piece, of the same workmanship--with gold, with blue, purple, and scarlet yarn, and with finely spun linen.

Exodus 39:20
They made two additional gold rings and attached them to the bottom of the two shoulder pieces of the ephod, on its front, near the seam just above its woven waistband.

Exodus 39:22
They made the robe of the ephod entirely of blue cloth, the work of a weaver,

And they did bind the breastplate by his rings to the rings of the ephod with a lace of blue, that it might be above the curious girdle of the ephod, and that the breastplate might not be loosed from the ephod; as the LORD commanded Moses.