Scala/Art Resource, New York, N.Y.

Tobias encounters a fish with magical powers in the Tigris River. Following the angel Raphael’s instructions, Tobit’s son Tobias catches the fish and keeps its gall, heart and liver to use as medicine. In this painting by Francesco Guardi (1712–1793), Raphael instructs Tobias, on the left, on fishing technique and later, shown in the background on the right, on how to gut the fish; the dog sits beside them, perhaps waiting for some bits to fall.

The Book of Tobit, probably written in the third century B.C.E., may have much older oral antecedents. Fragments in both Hebrew and Aramaic were found among the Dead Sea Scrolls at Qumran, but the earliest intact texts are Greek copies from the fourth or fifth century C.E.