Romans 3:9
Romans 3:99What then? Are we any better? Not at all. For we have already made the charge that Jews and Greeks alike are all under sin.
Watchtower commentary takes as describing the universal sinfulness inherited from Adam — "Jews as well as Greeks are all under sin." The verse is read as supporting the doctrine of inherited Adamic sin and the universal need for Christ's ransom. Salvation through the organisation is offered as the remedy for this universal condition.
This is Paul's verdict at the close of his prosecution. The promise of v7 ("everlasting life to those who… endure") and v10 ("glory and honour and peace for everyone who works what is good") describe a class. V9 names the class boundary: Jews and Greeks are all under sin — the class of perfect doers is empty. The verdict is universal because the standard is unreachable. And Paul's solution in v21-26 is also universal: "the righteousness of God through faith in Jesus Christ for all those having faith. For there is no distinction." The verdict's universality is matched by the rescue's universality. Christ saves the same class the law condemned — everyone, by faith.