A.T. Robertson Commentary Romans 9:23

"and that he might make known the riches of his glory upon vessels of mercy, which he afore prepared unto glory," — Romans 9:23 (ASV)

Vessels of mercy (σκευη ελεους). Objective genitive like σκευη οργης.

Afore prepared (προητοιμασεν). First aorist active indicative of προετοιμαζω, old verb to make ready (from ετοιμος, ready) and προ, before, in N.T. only here and Eph 2:10. But same idea in Ro 8:28-30.