Justification is by Faith Alone through Grace Alone.
The Epistle to Diognetus (2nd Century A.D.):
…He revealed (Himself) by faith, whereby alone it is given to see God. For God, the Master and Creator of the Universe, Who made all things and arranged them in order, was found to be not only friendly to men, but also long-suffering. And such indeed He was always, and is, and will be, kindly and good and dispassionate and true, and He alone is good. And having conceived a great and unutterable scheme He communicated it to His Son alone. For so long as He kept and guarded His wise design as a mystery, He seemed to neglect us and to be careless about us. But when He revealed it through His beloved Son, and manifested the purpose which He had prepared from the beginning, He gave us all these gifts at once, participation in His benefits, and sight and understanding of (mysteries) which none of us ever would have expected.
Having thus planned everything already in His mind with His Son, He permitted us during the former time to be borne along by disorderly impulses as we desired, led astray by pleasures and lusts, not at all because He took delight in. our sins, but because He bore with us, not because He approved of the past season of iniquity, but because He was creating the present season of righteousness, that, being convicted in the past time by our own deeds as unworthy of life, we might now be made deserving by the goodness of God, and having made clear our inability to enter into the kingdom of God of ourselves, might be enabled by the ability of God. And when our iniquity had been fully accomplished, and it had been made perfectly manifest that punishment and death were expected as its recompense, and the season came which God had ordained, when henceforth He should manifest His goodness and power (O the exceeding great kindness and love of God), He hated us not, neither rejected us, nor bore us malice, but was longsuffering and patient, and in pity for us took upon Himself our sins, and Himself parted with His own Son as a ransom for us, the holy for the lawless, the guileless for the evil, the just for the unjust, the incorruptible for the corruptible, the immortal for the mortal. For what else but His righteousness would have covered our sins? In whom was it possible for us lawless and ungodly men to have been justified, save only in the Son of God? O the sweet exchange, O the inscrutable creation, O the unexpected benefits ; that the iniquity of many should be concealed in One Righteous Man, and the righteousness of One should justify many that are iniquitous! Having then in the former time demonstrated the inability of our nature to obtain life, and having now revealed a Saviour able to save even creatures which have no ability, He willed that for both reasons we should believe in His goodness and should regard Him as nurse, father, teacher, counsellor, physician, mind, light, honour, glory, strength and life.
(The Epistle to Diognetus, 8-9; trans. J. B. Lightfoot, The Apostolic Fathers, ed. J. R. Harmer, [London: Macmillan and Co., Limited, 1912], pp. 508-509.)
But not by a Faith that is Alone.
The Epistle to Diognetus (2nd Century A.D.):
This faith if thou also desirest, apprehend first full knowledge of the Father. For God loved men for whose sake He made the world, to whom He subjected all things that are in the earth, to whom He gave reason and mind, whom alone He permitted to look up to heaven, whom He created after His own image, to whom He sent His only begotten Son, to whom He promised the kingdom which is in heaven, and will give it to those that have loved Him. And when thou hast attained to this full knowledge, with what joy thinkest thou that thou wilt be filled, or how wilt thou love Him that so loved thee before? And loving Him thou wilt be an imitator of His goodness. And marvel not that a man can be an imitator of God. He can, if God willeth it.
(The Epistle to Diognetus, 10; trans. J. B. Lightfoot, The Apostolic Fathers, ed. J. R. Harmer, [London: Macmillan and Co., Limited, 1912], p. 509.)
Further Reading.
Brandon D. Crowe, “Oh Sweet Exchange! The Soteriological Significance of Incarnation in the Epistle to Diognetus;” In: Zeitschrift für die neutestamentliche Wissenschaft und die Kunde der älteren Kirche, 102.1, [2011], pp. 96-109.
Brian J. Arnold’s Ph.D. Dissertation, “Justification One Hundred Years after Paul,” [Southern Baptist Theological Seminary, 2013], pp. 104-136.
D. H. Williams, “Justification by Faith: a Patristic Doctrine;” In: Journal of Ecclesiastical History, 57.4, [October 2006], p. 654.
George Stanley Faber, The Primitive Doctrine of Justification Investigated: Second Edition, [London: R. B. Seeley and W. Burnside, 1839], pp. 111-114.
Jordan Cooper, The Righteousness of One: An Evaluation of Early Patristic Soteriology in Light of the New Perspective on Paul, [Eugene: Wipf and Stock, 2013], pp. 90-96. Preview.
Michael F. Bird, “The Reception of Paul in The Epistle to Diognetus;” In: Paul and the Second Century, eds. Michael F. Bird, Joseph R. Dodson, [London: T&T Clark, 2011], pp. 85-88. Preview.
Nathan Busenitz, Long Before Luther: Tracing the Heart of the Gospel From Christ to the Reformation, [Chicago: Moody Publishers, 2017], pp. 96-97. Preview.
Thomas C. Oden, The Justification Reader, [Grand Rapids: William B. Eerdmans, 2002], p. 65.
Thomas R. Schreiner, Faith Alone: The Doctrine of Justification, [Grand Rapids: Zondervan, 2015], pp. 28-29. Preview.
καὶ αὐτός ἐστιν πρὸ πάντων καὶ τὰ πάντα ἐν αὐτῷ συνέστηκεν ~ Soli Deo Gloria