The ephod is used in this context (and elsewhere, see 1 Samuel 23:6) as a shorthand designation for the breastplate of the high priest that contained the Urim and the Thummim. The breastplate was attached to the ephod (garment) of the high priest (Exodus 28:4–14).1 The Urim and Thummim were two stones used to cast lots in order to discern God’s will. Most likely they were of different colouring and they would provide a yes
or a no
answer to specific questions.2 By these means the Lord provided guidance to the faithful kings under the old covenant.
7 And David said to Abiathar the priest, the son of Ahimelech, “Bring me the ephod.” So Abiathar brought the ephod to David.