This refers to the effect of Jesus' presence in the world. Without Jesus Christ, the world was mired in the shadow of death, but when Jesus Christ came, the light shone and the shadow dissipated. Jeremiah 13:16 says: Give glory to Jehovah your God, before he causes darkness to come, and before your feet stumble on mountains of darkness, and you look for light, and turn you into the shadow of death and darkness.
Once again, this text speaks to us of the shadow of death. In the Psalms, death is also spoken of as a shadow. Psalm 44:19 says: So that you may break us in the place of jackals,
And cover us with the shadow of death.