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.
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.