A curious term appeared in the Old Testament related to activities of the priests, especially in providing prophetic guidance as indicated in the 1 Samuel reference. The Exodus & Leviticus verses suggested that Unim could be an ornamental item since it was worn on the breastplate of the priest. The Jewish Virtual Library article suggested they were 12 gems corresponding to each of the tribes of Israel.
Exodus 28:30:
30. Also put the Urim and the Thummim in the breastpiece, so they may be over Aaron's heart whenever he enters the presence of the LORD. Thus Aaron will always bear the means of making decisions for the Israelites over his heart before the LORD.
Leviticus 8:8:
8. He placed the breastpiece on him and put the Urim and Thummim in the breastpiece.
Numbers 27:21:
21. He is to stand before Eleazar the priest, who will obtain decisions for him by inquiring of the Urim before the LORD. At his command he and the entire community of the Israelites will go out, and at his command they will come in."
Deuteronomy 33:8: (Moses' blessing of the priestly tribe of Levi)
8. About Levi he said: "Your Thummim and Urim belong to the man you favored. You tested him at Massah; you contended with him at the waters of Meribah.
1 Samuel 28:6:
6. He inquired of the LORD, but the LORD did not answer him by dreams or Urim or prophets.
Ezra 2:68:
63. The governor ordered them not to eat any of the most sacred food until there was a priest ministering with the Urim and Thummim.
Nehemiah 7:65:
65. The governor, therefore, ordered them not to eat any of the most sacred food until there should be a priest ministering with the Urim and Thummim.
The Ezra and Nehemiah verses seem to ask for the blessing of food by priests which led to the tradition of Jewish and Christian families praying for the food before a meal.
