But call to mind the former days, in which, after ye were enlightened, ye endured a great fight of afflictions; rather, conflict of sufferings. On φωτισθέντες ("enlightened"), cf. Hebrews 6:4, and what was said there as to the meaning of the word.
Here certainly the context seems naturally to suggest a definite reference to baptism, as marking the date of the commencement of exposure to persecution. But if so, not, of course, so as to exclude the idea of inward spiritual enlightenment.
"Hie primus erat ingressus ad Christianismum; baptismus apud idoneos salutare medium. Existimo haec instituta divina etiam in theoria non tanti aestimari quanti decebat. Apud ipsum baptismum Christi sancta ejus humanitas magnifice illuminata fuit" (Bengel).