IU 7

 Īśāvāsya Upaniṣad – Mantra 7 (often numbered 7 in standard recensions)

Sanskrit

यस्मिन् सर्वाणि भूतानि आत्मैवाभूद् विजानतः ।
तत्र को मोहः कः शोक एकत्वमनुपश्यतः ॥

Transliteration

yasmin sarvāṇi bhūtāni ātmaivābhūd vijānataḥ |
tatra ko mohaḥ kaḥ śoka ekatvamanupaśyataḥ ||

Translation (sense)

For one who truly understands:

• all beings are the Self alone,
• what delusion can remain there?
• what sorrow can there be,
• for one who sees unity everywhere?

Core meaning

This mantra expresses a central Upanishadic insight:

• When perception shifts from “many separate beings” to one underlying Self (Ātman),
• then fear, grief, and confusion lose their foundation, because they depend on separation.

It’s closely aligned with what you brought up earlier (Pratyabhijñā, non-dual consciousness):
both are pointing to the same structure of experience — suffering arises from perceived division; liberation is recognition of unity.

If you want,  I can also connect this directly to Pratyabhijñā’s idea of recognition (pratyabhijñā) vs this Upanishadic “seeing (anupaśyati)” — they’re almost mirror-language for the same shift.