Exodus 28:8
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 39:19
They made two other gold rings and put them at the two other corners of the breastpiece, on the inside edge next to the ephod.

Exodus 39:21
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 come loose from the ephod, just as the LORD had commanded Moses.