The Ten Bridesmaids
​​It seems clear that this parable is describing the same kind of thing that we see in the Banquet or the Weeds or the Net . That is, the kingdom of God is a complicated collection of good and evil (or, in this case, wise and foolish) until the end of the age, when everything is sorted out. 

In the custom of the day, the arrival of the bridegroom meant that the wedding was to begin. And as we see in other parables (notably the Talents and the Tenants ), the wait for the "God-character" (in this case "a long time in coming") is where the real drama takes place.

The wise bridesmaids brought extra oil for their lamps. The foolish bridesmaids did not. But even the foolish bridesmaids had every expectation to be granted access to the marriage feast (an ultimate blessing in Revelation 19:9 ) -- the only thing setting them apart from their already-partying friends was a short trip to the shop for more oil. Note that the foolish bridesmaids had enough oil to make it to the announcement of the bridegroom's arrival. Right up until that moment, there would have been nothing to distinguish them from the wise bridesmaids. 

But as in the parable of the Banquet (and this warning of Jesus ), there are those who expect to be invited into the feast of the kingdom, but who are forcefully kept outside. And the surprise involved in each of these cases challenges us to invest in "working out our salvation." In this parable, the foolish ones cry out, "Lord, Lord!" echoing the words Jesus uses in his famous sermon: "Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but only the one who does the will of my Father who is in heaven. ( Matthew 7:21 - see also this teaching )"

And as we read in Romans: "Do not conform to the pattern of this world, but be transformed by the renewing of your mind. Then you will be able to test and approve what God’s will is. (12:2)"

Matthew 25:1 (NLB) “Then the Kingdom of Heaven will be like ten bridesmaids who took their lamps and went to meet the bridegroom. 2 Five of them were foolish, and five were wise. 3 The five who were foolish didn’t take enough olive oil for their lamps, 4 but the other five were wise enough to take along extra oil. 5 When the bridegroom was delayed, they all became drowsy and fell asleep.
6 “At midnight they were roused by the shout, ‘Look, the bridegroom is coming! Come out and meet him!’
7 “All the bridesmaids got up and prepared their lamps. 8 Then the five foolish ones asked the others, ‘Please give us some of your oil because our lamps are going out.’
9 “But the others replied, ‘We don’t have enough for all of us. Go to a shop and buy some for yourselves.’
10 “But while they were gone to buy oil, the bridegroom came. Then those who were ready went in with him to the marriage feast, and the door was locked. 11 Later, when the other five bridesmaids returned, they stood outside, calling, ‘Lord! Lord! Open the door for us!’
12 “But he called back, ‘Believe me, I don’t know you!’
13 “So you, too, must keep watch! For you do not know the day or hour.