Matthew Poole and continuators on 1 Samuel 21:9

9 And the Priest said, The sword of Goliah the Philistine, whom thou slewest in the valley of Elah, behold, it is here wrapt in a cloth behind the Ephod : if thou wilt take that, take it, for there is no other save that, here. And David said, There is none like that , give it me.

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 Chap. 17.

Because it not onely served him for his use, for he was a Strong and Tall Man, and one that could wield that Sword, as we saw, Chap. 17. but was also a Pledge of God's Favour to him, and a great encouragement to his Faith.

Marginal references: Chap. 17. 2.