Exodus 39:20-22

New Revised Standard Version Catholic Edition

²⁰ They made two rings of gold, and attached them in front to the lower part of the two shoulder-pieces of the ephod, at its joining above the decorated band of the ephod. ²¹ They bound the breastpiece by its rings to the rings of the ephod with a blue cord, so that it should lie on the decorated band of the ephod, and that the breastpiece should not come loose from the ephod; as the Lord had commanded Moses.

²² He also made the robe of the ephod woven all of blue yarn;