Adam Clarke on Romans 8:21

Because the creature - This and the preceding verse should be thus connected: in hope That (ὁτι) the creature itself also shall be delivered. The word φθορα denotes, very frequently, sinful corruption. So, 2Pet 1:4 : Corruption through lust, της εν επιθυμια φθορας. 2Cor 11:3 : Lest your minds should be corrupted. 1Cor 15:33 : Evil communications corrupt good manners. The sense, therefore, of the apostle in this place seems to be: the Gentile world shall, in time, be delivered from the bondage of their sinful corruption, i.e. the bondage of their lusts and vile affections; and be brought into such a noble liberty as the sons of God enjoy.