And the leaders probably refers to the tribal “chiefs” (Revised English Bible). They are called the “leaders of the congregation” in 16.22 and 34.31. Brought onyx stones, literally “they caused to enter [or, come] the stones of onyx,” refers to the two stones to be placed on the shoulder straps of the ephod (28.9-12) and on the breastpiece of the high priest (28.20). The stones to be set, literally “stones of the setting,” were the twelve different kinds of stones for the breastpiece (28.17-20). (See the comment at 28.17.)

The spices were to be used for both the anointing oil (30.23-25) and the fragrant incense (30.34-35). They were not mixed with the oil for the light. (See 25.5 and the comment there.) The oil for the light, literally “oil for the luminary,” was olive oil, to be used in the lamps for the lampstand (25.37). It was also used in the recipe for the anointing oil (30.24). Contemporary English Version simply has a short summary of the lists of objects in verses 27 and 28, probably because they have all been listed in detail earlier:

• The leaders brought different kinds of jewels to be sewn on the special clothes and the breastpiece of the high priest. They also brought olive oil for the lamps and sweet-smelling spices to be mixed with the incense and with the oil for ordaining the priests.

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .