E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Valley of the Shadow of Death,
through which Christian had to pass in order to get to the Celestial City. The prophet Jeremiah describes it as a wilderness, a land of deserts and of pits, a land of drought and of the shadow of death (ii. 6); and the Psalmist says, Though I walk through the valley of the shadow of death, I will fear no evil, for Thou art with me; Thy rod and Thy staff they comfort me (xxiii. 4).
The light there is darkness, and the way full of traps and gins to catch the unwary.Bunyan: Pilgrims Progress, pt. i.