John Wesley on Deuteronomy 33:15

The chief things - That is, the excellent fruits, as grapes, olives, figs, &c. which delight in mountains, growing upon, or the precious minerals contained in, their mountains and hills called ancient and lasting, that is, such as have been from the beginning of the world, and are likely to continue to the end of it, in opposition to those hills or mounts which have been cast up by man.