In Shmos 28, G-d commanded to make the ephod and breastplate for the garments of the Kohen Gadol. G-d gave all the details connected to these two important items and named the twelve stones. Each of the stones carried the name of one of the twelve tribes of Israel. The high priest wore the breastplate on the ephod. When the people of Israel inquired of G-d concerning an important issue, the high priest asked G-d the question. G-d answered through the twelve stones. For example, when they wanted to know whether they should go out to war, the high priest asked G-d and G-d answered through the breastplate in this way: the relevant letters of the name of the tribe shone and together they formed G-d's answer. It was in this special way that G-d spoke to Israel.
The sages also found spiritual values and practical influences of the stones of the breastplate besides their holy task. Rabbi Bechayei said that each of the stones attracted heavenly strength, and in the Midrash in Bereshis Rabba 14 it is written that each of the stones receives strength from heaven. The Kabbala tells us that the twelve stones matched the attributes of the tribes.
The stone of Reuven, the Odem (ruby), is good for pregnant women, strengthens the heart and calms the mood; Shimon, the Piteda (topaz), cleanses the blood and teaches the benefit of the doubt; Levi, the Barekes (beryl), increases wisdom and aids learning; Yehudah, the Nofech (turquoise), calms the mood and removes worry; Yissachar, the Sapir (sapphire), strengthens the eyes and brings peace; Zevulun, Yahalom (diamond), brings longevity, and helps in earning a livelihood; Dan, Leshem (jacinth), strengthens a weak heart, brings joy and success to the wearer; Naftali, Shvo (agate), brings peace and happiness and repels the “evil eye”; Gad, Ahlama (jasper), gives strength and removes worry and fear; Asher, Tarshish (emerald), increases wisdom, gives courage and the wearer finds favor in the eyes of fellow men, and it brings success in business; Yosef, Shoham (onyx), is a remedy for restoring memory and improving sight, enables the wearer to speak wisely; Binyamin, Yashfe (jade), prevents hemorrhaging, improves sight and aids in childbirth.
