score:4
John Calvin in his commentary on Matthew encourages us to not get bogged down in the minutia of the parables. However, he essentially equates the oil to zeal.
Some people give themselves a good deal of uneasiness about the lamps, the vessels, and the oil; but the plain and natural meaning of the whole is, that it is not enough to have ardent zeal for a short time, if we have not also a constancy that never tires. And Christ employs a very appropriate parable to express this. A little before, he had exhorted the disciples, that as they had a journey to perform through dark and dreary places, they should provide themselves with lamps; but as the wick of the lamp, if it be not supplied with oil, gradually dries up, and loses its brightness, Christ now says, that believers need to have incessant supplies of courage, to support the flame which is kindled in their hearts, otherwise their zeal will fail ere they have completed the journey.