An interesting parable is found in Matthew.
Matthew 25:1 Then the kingdom of Heaven shall be compared to ten virgins who taking their lamps, went out to a meeting of the bridegroom.
2 And five of them were wise, and five foolish.
3 Those being foolish, taking their lamps, did not take oil with them.
4 But the wise took oil in their vessels with their lamps.
5 But the bridegroom delaying, all nodded and slept.
6 And at midnight, a cry occurred: Behold, the bridegroom comes! Go out to meet him.
7 Then all those virgins were aroused and prepared their lamps.
8 And the foolish said to the wise, Give us some of your oil, for our lamps are going out.
9 But the wise answered, saying, No, lest there not be enough for us and you. But rather, go to those who sell and buy for yourselves.
10 But they going away to buy, the bridegroom came. And those ready went in with him to the wedding feast, and the door was shut.
11 And afterwards, the rest of the virgins also came, saying, Lord, Lord, open to us.
12 But answering, he said, Truly I say to you, I do not know you.
13 Therefore, watch, for you do not know the day nor the hour in which the Son of Man comes.
Jesus is describing what it will be like when He suddenly comes to take His bride! He says, watch and be ready!
In Jewish weddings of that day, it was customary for the wedding party to be made up of girls to make the Bride more comfortable. These girls were waiting for the Groom to bring His Bride to his home. It was also necessary for the Groom to provide these "ladies in waiting" for the Bride if she had no friends to go with her or if she lived too far away. These girls were specifically there to light the way for the Groom and His Bride...therefore the lamps.
Lamps provide light for the feet and light the path--the Way to go. Jesus' emphasis was not on who these girls were. It was on the 5 girls that were ready to light the way. The lamps that were used for this purpose could only hold enough oil for about 15 minutes. Since the girls had no idea when the Bridegroom would arrive, the whole point here was on being ready with the light which meant extra oil would be needed if the groom didn't come within 15 minutes.
The oil could be the Holy Spirit; I have heard it preached that being ready with the oil meant those girls had the Holy Spirit and only those in possession of the Holy Spirit can go into the wedding feast. I'm not sure about that interpretation frankly. I need to pray about it some more. The parable is not about who the 10 girls are, but that the 5 who were ready and the other 5 were not ready, therefore since they were not ready the groom said "I do not know you!"
The unpardonable sin is not accepting Jesus as Savior. It is the only unforgivable sin. The 5 that were not prepared did not have Jesus as their Savior...they did not have the Oil and they did not have the Light.
Considered thoughts from Gina Burgess at 6:32 PM