SB 5.14.33
evam adhvany avarundhano mrtyu-gaja-bhayat tamasi giri-kandara-praye.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In this material world, when the conditioned soul forgets his relationship with the Supreme Personality of Godhead and does not care for Krsna consciousness, he simply engages in different types of mischievous and sinful activities. He is then subjected to the threefold miseries, and, out of fear of the elephant of death, he falls into the darkness found in a mountain cave.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Everyone is afraid of death, and however strong a materialistic person may be, when there is disease and old age one must certainly accept death’s notice. The conditioned soul becomes very morose to receive notice of death. His fear is compared to the fear experienced upon entering a dark mountain cave, and death is compared to a great elephant.