1 Samuel 23:9-11

Bring hither the ephod Which, doubtless, Abiathar put on; otherwise he could not have inquired of the Lord by it. The Lord said, He will come down He purposeth to come if thou continue here. For still both David's question and God's answer are conditional, upon supposition. As David's being there was the only motive for Saul's coming, so, if he departed, Saul could have no inducement to come. And accordingly we find he laid aside his design so soon as he was informed that David had escaped. It seems probable from this place that God's answer by Urim and Thummim was not by any change in the colour or situation of the precious stones in the breast-plate of the ephod, but by a voice or suggestion from God to the high-priest.