The Levite’s answer in Judges 18:4 should have disturbed the spies. They ought to have rebuked the Levite for working at the shrine of the apostate Micah. Instead, they are opportunists. The Levite's statement that he is a priest grabs their immediate attention, and they see what fortune this brings them. They are on a secret mission with no certainty of success. This priest can use the ephod to consult with God about their journey, and give them some sort of indication as to what lies ahead of them.
5 And they said to him, “Inquire of God, please, that we may know whether the journey on which we are setting out will succeed.”