Exodus 28:12

28:12 You are to put the two stones on the shoulders of the ephod, stones of memorial for the sons of Israel, and Aaron will bear their names before the Lord on his two shoulders for a memorial. ¹ 

Exodus 28:29

28:29 Aaron will bear the names of the sons of Israel in the breastpiece of decision over his heart ²  when he goes into the holy place, for a memorial before the Lord continually.

¹ sn This was to be a perpetual reminder that the priest ministers on behalf of the twelve tribes of Israel. Their names would always be borne by the priests.

² sn So Aaron will have the names of the tribes on his shoulders (v. 12) which bear the weight and symbol of office (see Isa 9:6; 22:22), and over his heart (implying that they have a constant place in his thoughts [Deut 6:6]). Thus he was to enter the presence of God as the nation’s representative, ever mindful of the nation’s interests, and ever bringing the remembrance of it before God (S. R. Driver, Exodus, 306).