In our Lord's parable, ten virgins await the coming of the the Bridegroom. Five of them are wise: they remembered to bring extra oil for their lamps. The five foolish virgins, on the other hand, neglected to do so. As a result, when the virgins were aroused from their slumber at midnight by someone crying that the Bridegroom had arrived, the five foolish ones asked the wise virgins to give them some of their oil, since their own lamps had gone out. This they would not do, however, lest by lending to the foolish ones, they themselves should run out of oil. Instead, they advised their foolish companions to go and buy some of their own.
Unfortunately, while the foolish virgins were out trying to find someone to sell them oil (and who could they find at that hour of the night?) the Bridegroom (that is, Christ) entered his chamber with the wise virgins and shut the door behind him. When at long last the foolish ones returned (presumably they had found some oil somewhere), they found the door shut and the Bridegroom saying, "I know you not."
Our Lord concludes His parable with this saying, "Watch, therefore, for ye know neither the day nor the hour wherein the Son of man cometh." Truly now is the day of salvation, during this brief earthly life while the door is still open for all those who choose to enter. On that Day when Christ returns to judge the living and the dead, it will be too late: the door will be closed forever. Likewise, the door of salvation will be closed for each and every one of us on that day when Christ calls us from this world and our souls are separated from our bodies and we go to stand naked and defenseless before the dread judgment seat.
What, then, is signified by the oil in the lamps? Some Church Fathers say the oil represents our good works during this life, and no doubt this is true. However, if we delve a little deeper, it might be said that the oil represents our good disposition toward God and all things needful for our salvation. After all, good deeds in themselves can be merely outward actions that mask an inner coldness toward God and our neighbor. Consider the philanthropist who gives money to worthy causes simply to salve his conscience or to gain the admiration of others. On the other hand, if one has a good disposition, good deeds will spring forth naturally and will truly gain for us heavenly treasures.
The door of salvation is open to those who have their hearts in the right place, hearts that are turned toward good with genuine humility and a spirit of repentance. Such a heart will be oriented toward God with an unquenchable love that is ever zealous to do His will. Moreover, a good heart is ever vigilant lest we lose our way on the path of salvation and fall prey to the Devil's deceptions.
Like a good soldier ever ready to do battle, we must be on guard at all times against carelessnes and deadly complacency, lest like the foolish virgins we find our lamps burning low on the day of reckoning. This means we should live every day of our lives as though it were our last, for truly it may well be. Then, like the foolish virgins, we will find ourselves unexpectantly and permanently shut out of the Kingdom, while the Bridegroom says, "I know you not." Then shall we be "cast out into that outer darkness in which there will be weeping and gnashing of teeth."