Romans 9:33

As it is written-- (Isa 8:14; Isa 28:16). Behold, &c.--Two Messianic predictions are here combined, as is not unusual in quotations from the Old Testament. Thus combined, the prediction brings together both the classes of whom the apostle is treating: those to whom Messiah should be only a stone of stumbling, and those who were to regard Him as the Cornerstone of all their hopes. Thus expounded, this chapter presents no serious difficulties, none which do not arise out of the subject itself, whose depths are unfathomable; whereas on every other view of it the difficulty of giving it any consistent and worthy interpretation is in our judgment insuperable. Note, (1) To speak and act "in Christ," with a conscience not only illuminated, but under the present operation of the Holy Ghost, is not peculiar to the supernaturally inspired, but is the privilege, and ought to be the aim, of every believer (Rom 9:1). (2) Grace does not destroy, but only intensify and elevate, the feelings of nature; and Christians should study to show this (Rom 9:2-3). (3) To belong to the visible Church of God, and enjoy its high and holy distinctions, is of the sovereign mercy of God, and should be regarded with devout thankfulness (Rom 9:4-5). (4) Yet the most sacred external distinctions and privileges will avail nothing to salvation without the heart's submission to the righteousness of God (Rom 9:31-33).

— Jamieson-Fausset-Brown Commentary (public domain)