Jesus told his disciples a parable about ten virgins: five who were wise and 5 who were foolish. The context of this parable is in the days of His return.
In this story, Jesus makes it clear that the wise were those who had gathered enough oil for their lamps to endure the delay of His coming. They had already been to the oil merchants and gathered a surplus of oil for their lamps and were prepared for the return of the Bridegroom though he was delayed in the late hours.
The oil in this parable is fuel for their lamps and speaks of the fuel for our hearts to maintain the flame as we are called to be burning and shining lamps in this age of growing darkness.