Ishavasya Upanishad- Verse 12 - Isha - 12-andhaṁ tamaḥ praviśanti

Ishavasya Upanishad – Verse 12 « »

अन्धं तमः प्रविशन्ति येऽसम्भूतिमुपासते ।
ततो भूय इव ते तमो य उ संभूत्यां रताः ॥ १२ ॥

andhaṃ tamaḥ praviśanti ye’sambhūtimupāsate |
tato bhūya iva te tamo ya u saṃbhūtyāṃ ratāḥ || 12 ||

12. They fall into blind darkness who worship the unborn Prakriti. They fall into greater darkness who are bent upon the Karya Brahman Hiranyagarbha. (12).

Commentary by Sri Adi Sankaracharya – Translated in English

Now, in view to the combining of the worship of the Avyakrita (Prakriti) and manifested Brahman, each in itself is denounced. “Asambhutih” is what is not Sambhutih or that which is born of another; hence unborn Prakriti. This again is ignorance, cause of all, known as Avyakrita. Those who worship this Prakriti, known as Avyakrita, ignorance which is the cause of all. the seed of all desire and Karma, and mere blindness in its nature, fall into corresponding or answering darkness which is blindness in its nature; and they who worship the Karya Brahman named Hiranyagarbha fall into even greater darkness.

Commentary by Swami Sivananda

Asambhutih is that which is not Sambhutih (born of another); uncreated nature, i.e., nature which has no cause; this is Avyakta or Avyakrita, the unmanifested nature, wherein three Gunas exist in a state of eilibrium (Guna-samya Avastha); matter and energy and the different kinds of sounds exist in an undifferentiated state. This is the cause of all. The whole world exists in a seed state in Avyaktam, just as the tree exists in the seed. Worship of this unmanifested Prakriti is known as Avyakta-upasana. Avyakta is also ignorance. It contains the seed of all desires and Karmas. Hiranyagarbha is Sambhuti or Karya Brahman. He is born of Avyakta. He is the effected of unmanifested Prakriti. Here is a beautiful interpretation of verses 1.1.12।। to 14 by Dr. Paul Deussen:-

Into dense darkness he enters
Who has conceived becoming to be naught,
Into yet denser he
Who has conceived becoming to be naught.
Different is it from coming into being;
Different also from not coming into being.
Thus have we from the ancient seers
Received the doctrine.
He who knows (as non-existent)
Both becoming and not-becoming
He passes through both
Beyond death, and has immortality.

Links
Commentary on the Isavasya Upanishad by Swami Krishnananda – Divine Life Society
Upanishad Series – Isavasya Upanishad Commentary by Swami Chinmayananda
Commentary on the Isavasya Upanishad by Paramarthananda

Ishavasya Upanishad – Verse 12 – Isha – 12-andhaṁ tamaḥ praviśanti – In Sanskrit with English Transliteration, Meaning and Commentary by Adi Shankaracharya (Sankara Bhashya) and Swami Sivananda – Ishavasya-12