There was once a man named Joseph who was famous in his city for one thing above all others: he honored the Shabbat. Every Friday his table groaned under fish and wine, whatever the week had been like. His neighbors called him Joseph the Sabbath Lover.
One of those neighbors, a Gentile, was very rich, and a fortune-teller told him a strange thing. In the end, all your property will pass into the hands of Joseph, the Jew who loves the Sabbath. The man resolved to outfox fate. He sold every field, every house, every vessel, and converted the whole estate into a single rare jewel, which he fastened to his turban. Now his wealth was portable, armored, and, he thought, safe from prediction.
One Friday he crossed a bridge, and a sudden gust blew the turban off his head and down into the river. A fish swallowed it. That fish was caught in a net, brought to market, and laid out as the choicest catch of the day. Joseph, preparing for the Sabbath, paid top price for it, because nothing was too good for his table on Friday. When the fish was cut open in his kitchen, the jewel rolled out. Joseph sold it for thirteen purses of gold denarii.
When the former neighbor met Joseph in the street, he conceded with a sigh, He who despises the Sabbath, the Lord of the Sabbath repays. And he who honors the Sabbath, the Lord of the Sabbath rewards. This tale from Shabbat 119a, preserved in Harris's 1901 Hebraic Literature, teaches that honoring Shabbat is not a weekly expense but an investment. Every fish you buy for a Friday night may be carrying a jewel.