What is the fundamental error in perception that, according to the scripture, keeps a soul bound to the cycle of death and rebirth?

According to the insights in Chapter 37, the fundamental error is the delusion caused by ignorance, which leads a person to feel separate from the ultimate reality. The text states that one who holds the knowledge of difference, thinking "Parabrahman is different from me; I am not that," is always subject to death. This perception of separateness is what perpetuates the eternal cycle of worldly existence (Samsara), where death follows birth and rebirth follows death, effectively trapping the soul.