‘The shadow of death’ is human life. Therefore if a man is with God and God is with him, clearly he is able to say, ‘Though I walk through the midst of the shadow of death, I will fear no evil’.
This passage delivers the most precise canonical definition in the corpus, equating the shadow of death with human life itself and grounding the term in Psalm 23’s promise that divine presence dissolves its terror.
, The Philokalia, Volume 2, 1981thesis