Exodus 35:27

The rulers brought onyx stones, and stones to be set. — The “rulers” here intended are probably the “princes of the tribes” of Israel (Numbers 1:16; Numbers 3:3; Numbers 3:5, &c.). The twelve stones required for the breastplate would naturally be contributed by the twelve chiefs of the tribes whose names they were to bear (Exodus 28:21). The two onyx stones for the ephod (Exodus 28:9), may have been the further gift of two of the number, who happened to possess stones of the large size needed.