The true goal of our Christian life consists of acquiring God’s Holy Spirit. Fasting and vigil, prayer, mercy, and every other good deed performed for Christ — are means for acquiring the Holy Spirit of God. Only deeds performed for Christ give us the fruits of the Holy Spirit.
Some say that the foolish virgins lacking enough oil in their lamps is meant to be understood as a lack of good deeds (see Mt. 25:1-12). Such an understanding is not completely correct. How could there have been a lack of good deeds when they, though foolish, are still called virgins? For virginity is the highest virtue, as a state equal to the angels, and could by itself serve in place of all other virtues. I, the wretched, think that they did not have enough of the grace of the All-Holy Spirit of God. These virgins, because of their spiritual injudiciousness, supposed in performing good deeds that it is only necessary to do good works to be a Christian: “We performed a good deed and thus did God’s will.” Whether or not they had received the grace of the Holy Spirit, whether they had attained it, they did not even bother to find out … But, this acquiring of the Holy Spirit is in fact that oil which the foolish virgins lacked. They are called foolish because they forgot about the essential fruit of virtue — the grace of the Holy Spirit — without which there is no salvation for anyone and cannot be. For “through the Holy Spirit every soul is quickened, and through its purification, it is exalted and illumined by the Triune Unity in a Holy mystery.” The Holy Spirit Himself settles in our souls, and this occupation of our souls by Him, the All-Ruling, and this coexistence of our spirit with His One Trinity, is granted only through the diligent acquiring, on our part, of the Holy Spirit, which prepares, in our soul and body, the throne for the coexistence of God the All-Creator with our spirit, by the immutable word of God: “And I will walk among you and will be your God, and ye shall be my people” (Lev. 26:12).
This is the very oil in the lamps of the wise virgins, which burned brightly and steadily; the virgins with these burning lamps could await the Groom coming at midnight, and enter the chamber of joy with him. The foolish ones, seeing their lamps going out, though they went to the market to buy oil, did not manage to return in time, for the doors were already locked. The market is our life; the doors of the bridal chamber — locked and not permitting entrance to the Groom — human death, the virgins wise and foolish, Christian souls; the oil, not deeds, but the grace of the All Holy Spirit of God received through them, transforming from decay to incorruption, from emotional death into spiritual life, from darkness to light, from the manger of our existence, where our passions are tied like beasts and animals, into a church of God, into the all-lighted chamber of eternal joy in Jesus Christ.”
– St. Seraphim of Sarov (emphasis mine)