Exodus 28:27-28

27Also make two gold rings and place them on the shoulder pieces of the ephod underneath, in the front, close to where it is joined, above the artfully woven band of the ephod.

28Then they will bind the breastplate by its rings to the rings of the ephod with a blue thread, so that it may be on the skillfully woven band of the ephod, and so that the breastplate will not come loose from it.