Mandukya Karika, verse 4.10


जरामरणनिर्मुक्ताः सर्वे धर्माः स्वभावतः ।
जरामरणमिच्छन्तश्च्यवन्ते तन्मनीषया ॥ १० ॥

jarāmaraṇanirmuktāḥ sarve dharmāḥ svabhāvataḥ |
jarāmaraṇamicchantaścyavante tanmanīṣayā || 10 ||

10. All the Jīvas are, by their very nature, free from senility and death. They think, as it were, that they are subject to these and thus by this very thought they appear to deviate from their very nature.

Shankara Bhashya (commentary)

What is the basis of that Prakṛti whose change is imagined by the disputants? What, again, is the defect in such imagination? This is thus replied:—The words “Free from senility and death,” in the text signify freedom from all changes1 characterised by senility, death, etc. Who are thus free (from all changes)? These are all the Jīvas, who are, by their very nature, free from all changes. Though the Jīvas are such by their very nature, yet they think, as it were, that they are subject to senility and death. By such imagination2 about their selves, like the imagination of the snake in the rope, they (appear to) deviate from their nature. This happens on account of their identification, through thinking, with senility and death. That is to say, they (appear to) fall from their real nature by this defect in their thought.