28 The rings of the breastpiece are to be tied to the rings of the ephod with blue cord, connecting it to the waistband, so that the breastpiece will not swing out from the ephod.

Read Exodus 28:28 Using Other Translations

And they shall bind the breastplate by the rings thereof unto the rings of the ephod with a lace of blue, that it may be above the curious girdle of the ephod, and that the breastplate be not loosed from the ephod.
And they shall bind the breastpiece by its rings to the rings of the ephod with a lace of blue, so that it may lie on the skillfully woven band of the ephod, so that the breastpiece shall not come loose from the ephod.
Then attach the bottom rings of the chestpiece to the rings on the ephod with blue cords. This will hold the chestpiece securely to the ephod above the decorative sash.