Mandukya Karika 4.9

सांसिद्धिकी स्वाभाविकी सहजा अकृता च या ।
प्रकृतिः सेति विज्ञेया स्वभावं न जहाति या ॥ ९ ॥

sāṃsiddhikī svābhāvikī sahajā akṛtā ca yā |
prakṛtiḥ seti vijñeyā svabhāvaṃ na jahāti yā || 9 ||

9. By prakṛti or the inherent nature of a thing is understood that which, when acquired, becomes completely part and parcel of the thing, that which is its very characteristic quality, that which is part of it from its very birth, that which does not depend upon anything extraneous for its origin and that which never ceases to be itself.

Shankara Bhashya (commentary)

Even¹ the nature of a thing in ordinary experience does not undergo any reversal. What is meant by the nature of a thing? This is thus replied:—The word “samsiddhi” means “complete attainment”. The nature of a thing is formed by such complete attainment as in the case of the perfected Yogis who attain to such superhuman powers as Aṇimā,² etc. These powers thus acquired by the Yogis never undergo any transformation in the past and future. Therefore these constitute the very nature of the Yogis, Similarly, the characteristic quality of a thing, such as heat or light of fire and the like, never undergoes any change either in time or space. So also the nature of a thing which is part of it from its very birth, as the flying power of the bird, etc., through the sky, is called its prakṛti. Anything else which is not produced by any other cause (except the thing itself); such as the running downwards of water is also called prakṛti. And lastly, anything which³ does not cease to be itself is known popularly to be its prakṛti. The purport of the Kārikā is that if in the case of empirical entities, which are only imagined,⁴ their nature or prakṛti does not undergo any change, then how should it be otherwise in the case of the immortal or unchanging nature regarding the Ultimate Reality, whose very Prakṛti is Ajāti or absolute non-manifestation.

Anandagiri Tika (glossary)

¹ Even, etc.—The purport is that if the unchangeability of the nature of a thing is noticed in ordinary experiences, then it applies with greater force to Brahman whose changeless and immortal nature can never undergo any transformation.

² Aṇimā—There are eight superhuman powers which the Yogis can attain to as the result of their yogic perfection. The word ‘Aṇimā’ means the power of becoming as small as an atom.

³ Which, etc.—As the characteristics of a jar or the jar? ness of it which depends entirely upon the jar and not upon anything else.

⁴ Imagined— According to Advaita Vedānta the characteristics of entities of ordinary experience which are thought of as unchanging by the dualists, are mere imagination.