Sforno on Exodus 28:2/ספורנו על שמות כ״ח:ב׳

1לכבוד, to render honour and glory to the Almighty through the wearing of such resplendent garments when performing Temple service.

2ולתפארת, also the Priest should inspire awe among the Israelites who are all considered his disciples seeing he had the names of all the tribes engraved on these garments right opposite his heart when he wore them in his official capacity.