"The Roman Catholic writer Joseph A. Fitzmyer points out that Luther was not the only one to translate Romans 3:28 with the word “alone.”
At 3:28 Luther introduced the adv. “only” into his translation of Romans (1522), “alleyn durch den Glauben” (WAusg 7.38); cf. Aus der Bibel 1546, “alleine durch den Glauben” (WAusg, DB 7.39); also 7.3-27 (Pref. to the Epistle). See further his Sendbrief vom Dolmetschen, of 8 Sept. 1530 (WAusg 30.2 [1909], 627-49; “On Translating: An Open Letter” [LuthW 35.175-202]). Although “alleyn/alleine” finds no corresponding adverb in the Greek text, two of the points that Luther made in his defense of the added adverb were that it was demanded by the context and that sola was used in the theological tradition before him.
Robert Bellarmine listed eight earlier authors who used sola (Disputatio de controversiis: De justificatione 1.25 [Naples: G. Giuliano, 1856], 4.501-3):
Origen, Commentarius in Ep. ad Romanos, cap. 3 (PG 14.952).
Hilary, Commentarius in Matthaeum 8:6 (PL 9.961).
Basil, Hom. de humilitate 20.3 (PG 31.529C).
Ambrosiaster, In Ep. ad Romanos 3.24 (CSEL 81.1.119): “sola fide justificati sunt dono Dei,” through faith alone they have been justified by a gift of God; 4.5 (CSEL 81.1.130).
John Chrysostom, Hom. in Ep. ad Titum 3.3 (PG 62.679 [not in Greek text]).
Cyril of Alexandria, In Joannis Evangelium 10.15.7 (PG 74.368 [but alludes to Jas 2:19]).
Bernard, In Canticum serm. 22.8 (PL 183.881): “solam justificatur per fidem,” is justified by faith alone.
Theophylact, Expositio in ep. ad Galatas 3.12-13 (PG 124.988).
Source: Joseph A. Fitzmyer Romans, A New Translation with introduction and Commentary, The Anchor Bible Series (New York: Doubleday, 1993) 360-361."