असतो मायया जन्म तत्त्वतो नैव युज्यते ।
वन्ध्यापुत्रो न तत्त्वेन मायया वाऽपि जायते ॥ २८ ॥asato māyayā janma tattvato naiva yujyate |
vandhyāputro na tattvena māyayā vā’pi jāyate || 28 ||28. The unreal cannot be born either really or through Māyā. For the son of a barren woman is born neither in reality nor in illusion.
Shankara Bhashya (commentary)
There are those who hold that all entities are unreal, that the non-existent produces this world. But production, by the non-existent, of any thing either in reality or in illusion is not possible. For we know nothing like it in our experience. As the son of a barren woman is not seen to be born either really or through Māyā, the theory of the non-existence of things is in truth1 untenable.
Anandagiri Tika (glossary)
If the ultimate Reality be non-existent, then it cannot pass into birth. Again if what we perceive be unreal, its production is likewise impossible. In either case causality is unreal. We have seen from the previous Kārikā (27) that the Reality, which is the unborn Ātman, cannot be said to pass into birth, without our being forced into an infinite regress. This Kārikā shows that production is an impossibility if the ultimate Reality be non-existent, or if the thing we perceive be unreal. So, causality or production or passing into birth is an absurdity.
1 In truth—In case the Ātman is a Reality, the passing into birth may be explained by Māyā; but in this case even that explanation cannot hold, for there is no evidence in our actual experience to justify the presumption that either something comes out of nothing or nothing comes out of something.