Flasks of oil (Good News Translation “containers full of oil for their lamps”) is translated “oil for refilling” by Die Bibel im heutigen Deutsch; one may even translate “extra oil.” The flasks were probably pottery containers. Sometimes “jar” is used, but other translations use general terms, such as “container” or “container for oil.”

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on the Gospel of Matthew. (UBS Handbook Series). New York: UBS, 1988. For this and other handbooks for translators see here .