In 1 Clement 32.3-4 (probably written just before 100 AD), we get a great Pauline statement on justification by faith only.
“All (the OT saints) therefore were glorified and magnified, not through themselves or their own works or the righteous actions that they did, but through His will. And so we, having been called through His will in Christ Jesus, are not justified (dikaioumetha) through ourselves or through our own wisdom or understanding or piety (eusebeias), or works (ergon) that we have done in holiness of heart, but through faith (dia tes pisteos), by which the Almighty God has justified (edikaiosen) all who have existed from the beginning; to whom be the glory for ever and ever. Amen.”
This is a great statement. Earlier in ch. 32, the author was talking about God’s gifts given in the OT era (Jacob, Levites, etc). He ties the OT saints to the NT (and beyond) saints saying they were all justified by faith, not works or piety.