The earliest surviving literary source for the Greek myth of Pandora’s container is Hesiod’s Works and Days.
Hesiod’s poem, generally dated to the late eighth or early seventh century BCE, tells how Zeus creates Pandora as part of a punishment connected with Prometheus and fire. Pandora later opens a storage vessel, releasing sufferings into the human world while one force remains inside.
The poem is not primarily a collection of myths. Works and Days combines advice about farming, justice, labor, seafaring, and the proper organization of life with stories that explain why human existence is difficult. Pandora’s episode appears in that broader moral and economic context.
Hesiod also wrote the Theogony, which mentions Pandora but does not give the complete container-opening narrative. The Iliad and Odyssey are earlier in the epic tradition, but neither provides the familiar Pandora story. This is why Works and Days is the key source for the specific myth.