Fasten the two stones upon the shoulder pieces of the ephod, to be memorial stones for Bnei-Yisrael. So Aaron is to bear their names before Adonai on his two shoulders as a reminder.
just as Adonai had spoken to him by Moses’ hand, so that it would be as a reminder to Bnei-Yisrael that no one who was not a descendant of Aaron should burn incense before Adonai, and so no one would become like Korah and his following.