1 Samuel 21:9

Behind the ephod, i.e. behind that holy place allotted for the keeping of the sacred or priestly garments; all which are here comprehended under the ephod; which, as the chief of the kind, is put for all the rest. Here it was laid up as a sacred monument of God's power and goodness, and that famous victory, related 1Sa 17. There is none like that; because it not only served him for his use, for he was a strong and tall man, and one that could wield that sword, as we saw, 1Sa 17, but was also a pledge of God's favour to him, and a great encouragement to his faith.