Mandukya Karika, verse 4.29


अजातं जायते यस्मात् अजातिः प्रकृतिस्ततः ।
प्रकृतेरन्यथाभावो न कथंचिद्भविष्यति ॥ २९ ॥

ajātaṃ jāyate yasmāt ajātiḥ prakṛtistataḥ |
prakṛteranyathābhāvo na kathaṃcidbhaviṣyati || 29 ||

29. (In the opinion of the disputants) that which is unborn is said to be born. For, its very nature is to be ever unborn. It is never possible for a thing to be other than what it is.

Shankara Bhashya (commentary)

For reasons already stated it is established that Brahman is one and unborn. This verse summarises, the conclusion of what has already been stated in the form of proposition. The unborn mind, which1 is verily Brahman, is imagined by the disputants to be born. Therefore (according to them) the ever-unborn is said to be born. For, it is unborn by its very nature. It2 is simply impossible for a thing, which is ever unborn by nature, to be anyhow born, that is to say, to be anyhow otherwise than what it is.