Mandukya Karika, verse 4.74


अजः कल्पितसंवृत्या परमार्थेन नाप्यजः ।
परतन्त्रादिनिष्पत्त्या संवृत्या जायते तु सः ॥ ७४ ॥

ajaḥ kalpitasaṃvṛtyā paramārthena nāpyajaḥ |
paratantrādiniṣpattyā saṃvṛtyā jāyate tu saḥ || 74 ||

74. Ātman is called unborn (Aja) from the standpoint of the illusory empirical experiences. It is, truly speaking, not even unborn. That unborn Ātman appears to be born from the standpoint of the belief of the other schools of thought.

Shankara Bhashya (commentary)

(Objection)—If Scriptural teaching, etc., were illusory, then the birthlessness of Ātman, as taught by Scripture, is also due to illusory imagination. (Reply)—This is, indeed, true. Ātman is said to be unborn only in relation to illusory empirical experiences which comprehend ideas of Scripture, teacher and taught. From1 the standpoint of the Ultimate Reality, Ātman cannot be said to be even unborn. Ātman 2 which is said to be unborn only as against the conclusion of those schools (which maintain that Ātman comes into existence), appears to be born to the ignorant. Therefore, the notion (based upon illusion) that Ātman is unborn has no bearing on the Ultimate Reality.