Origen — as excerpted in the Catena Aurea on Matthew 25:1-13

“Or, The oil is the word of teaching, with which the vessels of souls are filled; for what gives so great content as moral discourse, which is called the oil of light. The wise took with them of this oil, as much as would suffice, though the Word should tarry long, and be slack to come to their consummation. The foolish took lamps, alight indeed at the first, but not supplied with so much oil as should suffice even to the end, being careless respecting the provision of doctrine which comforts faith, and enlightens the lamp of good deeds.”