a widow's cruse
a widow's crusean apparently small supply that proves inexhaustible.
In the Bible, 1 Kings 17 tells the story of the widow to whom Elijah was sent for sustenance. When he asked her for bread, she replied that all she had for herself and her son was ‘an handful of meal in a barrel and a little oil in a cruse’ (a cruse was a small earthenware pot or jar). Elijah told her to make him a cake from these ingredients and then to make food for herself and her son as God had decreed that the containers should be continually replenished.