This parable is one of the most important in all of Scripture, and a proper understanding of it is crucial. The interpreter par-excellence of this Gospel is my Patron, St Seraphim of Sarov. His “Conversation with Motovilov” (also here) contains pearls regarding this parable.
Then shall the kingdom of heaven be likened unto ten virgins, which took their lamps, and went forth to meet the bridegroom. (2) And five of them were wise, and five were foolish. (3) They that were foolish took their lamps, and took no oil with them: (4) But the wise took oil in their vessels with their lamps. (5) While the bridegroom tarried, they all slumbered and slept. (6) And at midnight there was a cry made, Behold, the bridegroom cometh; go ye out to meet him. (7) Then all those virgins arose, and trimmed their lamps. (8) And the foolish said unto the wise, Give us of your oil; for our lamps are gone out. (9) But the wise answered, saying, Not so; lest there be not enough for us and you: but go ye rather to them that sell, and buy for yourselves. (10) And while they went to buy, the bridegroom came; and they that were ready went in with him to the marriage: and the door was shut. (11) Afterward came also the other virgins, saying, Lord, Lord, open to us. (12) But he answered and said, Verily I say unto you, I know you not. (13) Watch therefore, for ye know neither the day nor the hour wherein the Son of man cometh. (Mat 25:1-13)
Prayer, fasting, vigil and all other Christian activities, however good they may be in themselves, do not constitute the aim of our Christian life, although they serve as the indispensable means of reaching this end. The true aim of our Christian life consists in the acquisition of the Holy Spirit of God. As for fasts, and vigils, and prayer, and almsgiving, and every good deed done for Christ's sake, they are only means of acquiring the Holy Spirit of God. But mark, my son, only the good deed done for Christ's sake brings us the fruits of the Holy Spirit. All that is not done for Christ's sake, even though it be good, brings neither reward in the future life nor the grace of God in this. That is why our Lord Jesus Christ said: He who gathers not with Me scatters (Luke 11:23). Not that a good deed can be called anything but gathering, since even though it is not done for Christ's sake, yet it is good. Scripture says: In every nation he who fears God and works righteousness is acceptable to Him.
"In the parable of the wise and foolish virgins, when the foolish ones lacked oil, it was said: 'Go and buy in the market.' But when they had bought, the door of the bride-chamber was already shut and they could not get in. Some say that the lack of oil in the lamps of the foolish virgins means a lack of good deeds in their lifetime. Such an interpretation is not quite correct. Why should they be lacking in good deeds if they are called virgins, even though foolish ones? Virginity is the supreme virtue, an angelic state, and it could take the place of all other good works.
"I think that what they were lacking was the grace of the All-Holy Spirit of God. These virgins practiced the virtues, but in their spiritual ignorance they supposed that the Christian life consisted merely in doing good works. By doing a good deed they thought they were doing the work of God, but they little cared whether they acquired thereby the grace of God's Spirit. Such ways of life based merely on doing good without carefully testing whether they bring the grace of the Spirit of God, are mentioned in the Patristic books: 'There is another way which is deemed good at the beginning, but it ends at the bottom of hell.'
"Antony the Great in his letters to Monks says of such virgins: 'Many Monks and virgins have no idea of the different kinds of will which act in man, and they do not know that we are influenced by three wills: the first is God's all-perfect and all-saving will: the second is our own human will which, if not destructive, yet neither is it saving; and the third is the devil's will—wholly destructive.'
And this third will of the enemy teaches man either not to do any good deeds, or to do them out of vanity, or to do them merely for virtue's sake and not for Christ's sake. The second, our own will, teaches us to do everything to flatter our passions, or else it teaches us like the enemy to do good for the sake of good and not care for the grace which is acquired by it. But the first, God's all-saving will, consists in doing good solely to acquire the Holy Spirit, as an eternal, inexhaustible treasure which cannot be rightly valued. The acquisition of the Holy Spirit is, so to say, the oil which the foolish virgins lacked. They were called foolish just because they had forgotten the necessary fruit of virtue, the grace of the Holy Spirit, without which no one is or can be saved, for: 'Every soul is quickened by the Holy Spirit and exalted by purity and mystically illumined by the Trinal Unity.'
"This is the oil in the lamps of the wise virgins which could burn long and brightly, and these virgins with their burning lamps were able to meet the Bridegroom, Who came at midnight, and could enter the bridechamber of joy with Him. But the foolish ones, though they went to market to buy some oil when they saw their lamps going out, were unable to return in time, for the door was already shut.
The market is our life;the door of the bridechamber which was shut and which barred the way to the Bridegroom is human death;
the wise and foolish virgins are Christian souls;the oil is not good deeds but the grace of the All-Holy Spirit of God which is obtained through them and which changes souls from one state to another—that is, from corruption to incorruption, from spiritual death to spiritual life, from darkness to light, from the stable of our being (where the passions are tied up like dumb animals and wild beasts) into a Temple of the Divinity, into the shining bridechamber of eternal joy in Christ Jesus our Lord, the Creator and Redeemer and eternal Bridegroom of our souls.