Clement of Alexandria — Stromata 6

But as the proclamation [of the Gospel ] has come now at the fit time, so also at the fit time were the Law and the Prophets given to the Barbarians, and Philosophy to the Greeks, to fit their ears for the Gospel . Therefore, says the Lord who delivered Israel , in an acceptable time have I heard you, and in a day of salvation have I helped you. And I have given you for a Covenant to the nations; that you might inhabit the earth, and receive the inheritance of the wilderness; saying to those that are in bonds, Come forth; and to those that are in darkness, Show yourselves.

For if the prisoners are the Jews , of whom the Lord said, Come forth, you that will, from your bonds, — meaning the voluntary bound, and who have taken on them the burdens grievous to be borne Matthew 23:4 ; Luke 11:46 by human injunction — it is plain that those in darkness are they who have the ruling faculty of the soul buried in idolatry . For to those who were righteous according to the law, faith was wanting. Wherefore also the Lord, in healing them, said, Your faith has saved you. But to those that were righteous according to philosophy , not only faith in the Lord , but also the abandonment of idolatry , were necessary. Straightway, on the revelation of the truth , they also repented of their previous conduct. Wherefore the Lord preached the Gospel to those in Hades.

Accordingly the Scripture says, Hades says to Destruction, We have not seen His form, but we have heard His voice. It is not plainly the place, which, the words above say, heard the voice, but those who have been put in Hades, and have abandoned themselves to destruction, as persons who have thrown themselves voluntarily from a ship into the sea. They, then, are those that hear the divine power and voice. For who in his senses can suppose the souls of the righteous and those of sinners in the same condemnation, charging Providence with injustice ? But how? Do not [the Scriptures ] show that the Lord preached the Gospel to those that perished in the flood, or rather had been chained, and to those kept in ward and guard ?

1 Peter 3:19-20 And it has been shown also, in the second book of the Stromata , that the apostles , following the Lord, preached the Gospel to those in Hades. For it was requisite, in my opinion, that as here, so also there, the best of the disciples should be imitators of the Master; so that He should bring to repentance those belonging to the Hebrews, and they the Gentiles ; that is, those who had lived in righteousness according to the Law and Philosophy, who had ended life not perfectly, but sinfully.