Jesus told his disciples this parable:
"The kingdom of heaven will be like ten virgins who took their lamps and went out to meet the bridegroom. Five of them were foolish and five were wise. The foolish ones, when taking their lamps, brought no oil with them, but the wise brought flasks of oil with their lamps. Since the bridegroom was long delayed, they all became drowsy and fell asleep. At midnight, there was a cry, 'Behold, the bridegroom! Come out to meet him!' Then all those virgins got up and trimmed their lamps.  The foolish ones said to the wise, 'Give us some of your oil, for our lamps are going out.' But the wise ones replied, 'No, for there may not be enough for us and you. Go instead to the merchants and buy some for yourselves.' While they went off to buy it, the bridegroom came and those who were ready went into the wedding feast with him. Then the door was locked. Afterwards the other virgins came and said, 'Lord, Lord, open the door for us!' But he said in reply, 'Amen, I say to you, I do not know you.' Therefore, stay awake, for you know neither the day nor the hour."