Carl F. H. Henry wrote in his magnum opus God, Revelation, and Authority (Crossway, 1999), 4:56:
In many ways the early Christians undoubtedly reflected the sociological context in which they lived. Presumably the disciples and apostles followed current modes of dress, hair-styling, as well as other social customs; their public attestation of Christian faith surely did not escape some cultural conditioning of language and idiom, manner and mores. Yet we know too little about sociological conditions in the first-century Greco-Roman world to draw up any confident listing of what must and must not have been merely cultural behavior on the part of the early Christians.
Even if we conclude that some given practice is culturally derived, where such a practice was followed or avoided as a higher matter of Christian duty, we still face the implicit recognition of an eternally valid moral principle grounded in divine revelation. The expression of that principle might indeed vary from culture to culture, but that variation would not lessen the principle’s significance simply to a matter of sociological conformity.
While I think modern discoveries will continue to bring new clarity to the Greco-Roman world of the New Testament, Henry’s main point is an important one. Despite the many discontinuities that exist between the NT culture and our own, we discover in Scripture certain ethical contexts where “an eternally valid moral principle” is in play, a principle that can be discerned and then given a modern application. The pastor’s task is to answer these questions, writes Henry: “What permanent principle undergirds the apostolic teaching? Is that principle best promoted today by the practice or procedure indicated in apostolic times? If it is not, what alternative preserves the biblical intention?”