"Command the Israelites to bring you clear oil of pressed olives for the light so that the lamps may be kept burning. In the tent of meeting, outside the curtain that shields the ark of the covenant law, Aaron and his sons are to keep the lamps burning before the LORD from evening till morning. This is to be a lasting ordinance among the Israelites for the generations to come" (Ex 27:20-21).
The lamps were not allowed to go out in the temple––continually maintained by the priests, and supplied with fuel given by God's people––they burned night and day.
It's a picture of covenant faithfulness––one of the ways the Law was a tutor (Gal. 3:24).
Jesus invoked such imagery in the parable of the ten maidens. They were all dressed for the feast, they all had lamps with oil, and were concerned about the groom’s coming, and they all fell asleep while he delayed (Matt. 25:1-13).
It is only when he is announced that any difference becomes apparent. The ones who were prepared (brought oil along) were able to enter the feast with the groom, while the others were left to find more oil. A lamp without oil is essentially useless, isn’t it? It may have some aesthetic value, but it cannot serve its real purpose, only outward appearances. Likewise, faith without works is useless (Jas. 2:17). The unprepared women desired the oil of those who were prepared, but genuine faithfulness (faith working through love, Gal 5:6) has never been transferable. Thus the foolish women are told to “go to those who sell, and buy for yourselves” (Matt. 25:9). We read in Romans 14:12 that "each one shall give an account of HIMSELF to God," just as every Israelite had to bring oil to keep the lamps burning. It is not enough to be a member of a local church outwardly––in name only––one must be genuinely working and preparing for the Lord's return. The foolish maidens who ran out of lamp oil before the bridegroom returned, had no recourse when the time came. "Let your light shine before men, that they may see your good deeds and glorify your Father in heaven" (Matt. 5:16). The lamps must be kept burning.