Albert Barnes Commentary 1 Samuel 30:7

"And David said to Abiathar the priest, the son of Ahimelech, I pray thee, bring me hither the ephod. And Abiathar brought thither the ephod to David." — 1 Samuel 30:7 (ASV)

Abiathar had continued to remain with David ever since he joined him at Keilah (1 Samuel 23:6). Regarding inquiring of the Lord by the ephod, see the note on Judges 1:1. The answers were evidently given by the Word of the Lord in the mouth of the high priest .