NOTES for Еф 5:1-21
When speaking about spiritual life, Paul never tires of repeating that the fullness of the Kingdom is incompatible with any sin (vv. 3-7). Such persistent reminders of this obvious fact were evidently connected with the fact that for many Christians (and, perhaps, not only in Ephesus) it was not obvious at all. Judging by some of the apostle's instructions in his letter to the Ephesian Christians, they were evidently already prepared to accept as normal that sin would remain, to some extent, part of their life (vv. 1-3, 15-21).
This was connected to the fact that many in the Ephesian church looked at Christianity not as life in the Kingdom but as a new religion, perhaps as a distinctive form of Judaism for Gentiles. In that case one would have to make peace with the presence of sin in the life of the faithful, because there are no sinless people, and Judaism never required the impossible from a person. It required only the absolute exclusion of sin committed consciously and voluntarily, not every sin in general. The latter was an unattainable ideal toward which one could and should strive, but which could not be demanded of anyone as the norm of life.
Apparently the Christians of Ephesus looked at the matter in the same way, accepting as a given the sins of some of their brothers. Paul, however, understands perfectly that Christianity is not a new religion at all, but precisely life in the Kingdom, and therefore he insists on the ideal that in the Kingdom can and must become reality. He knows that for a Christian sin means not only deviation from the path of righteousness, but also the loss of the Kingdom, which is not always noticeable at once only because the Kingdom has not yet been fully revealed in our transforming but still untransformed world. The one who sins truly finds himself in that outer darkness which the Savior Himself contrasts with the Kingdom, and if he does not always realize it, that is only because he still has the opportunity to avoid both the final choice that he will have to make at the Last Judgment and the full consequences of the sin he has committed, consequences that remain hidden from a person until the end of time.
But Paul calls his readers to look at the situation through the eyes of a person for whom the end of time has already arrived, and to evaluate each of their actions accordingly, so as to become inhabitants of the Kingdom in full measure here and now.