Urim and Thummim were jeweled ornaments worn by the high priest over his ephod. Jewels symbolizing the twelve tribes of Israel were suspended from them, but their exact shape or material has not been definitively passed down. It is stated that God's will was discerned through these Urim and Thummim, but the exact method for doing so is also not described.
Numbers 27:21Moses did as Yahweh commanded him. He took Joshua, and set him before Eleazar the priest and before all the congregation.
1 Samuel 28:6Then Saul said to his servants, “Seek for me a woman who has a familiar spirit, that I may go to her, and inquire of her.” His servants said to him, “Behold, there is a woman who has a familiar spirit at Endor.”
Leviticus 8:8He set the turban on his head. He set the golden plate, the holy crown, on the front of the turban, as Yahweh commanded Moses.
Exodus 28:30“You shall make the robe of the ephod all of blue.
