Abiathar had continued to abide with David, ever since he joined him at Keilah 1 Samuel 23:6. On inquiry of the Lord by the ephod, see Judges 1:1 note. The answers were evidently given by the Word of the Lord in the mouth of the high priest (compare John 11:51).
Related Commentaries of 1 Samuel 30:7
1 Samuel 30:7
7 And David said to Abiathar the priest, Ahimelech's son, I pray thee, bring me hither the ephod. And Abiathar brought thither the ephod to David.