Verse 1.2.6

अथ ह मन उद्गीथमुपासांचक्रिरे तद्धासुराः पाप्मना विविधुस्तस्मात्तेनोभयंसंकल्पते संकल्पनीयंच चासंकल्पनीयं च पाप्मना ह्येतद्विद्धम् ॥ १.२.६ ॥

atha ha mana udgīthamupāsāṃcakrire taddhāsurāḥ pāpmanā vividhustasmāttenobhayaṃsaṃkalpate saṃkalpanīyaṃca cāsaṃkalpanīyaṃ ca pāpmanā hyetadviddham || 1.2.6 ||

6. Next, the gods and goddesses worshipped the mind, because the mind makes it possible for them to chant the udgītha [the praise to Om]. But the demons even vitiated the mind. As a result, the mind has both good and bad thoughts. This happens because of ignorance.

Word-for-word explanation:

Atha ha, next; manaḥ udgītham upāsāñcakrire, [the gods and goddesses] worshipped the mind for its role in chanting the udgītha; asurāḥ ha, the asuras, however; tat, that [mind]; pāpmanā vividhuḥ, poisoned it with bad thoughts; tasmāt, for that reason; tena, in the mind; ubhayam saṅkalpanīyam ca asaṅkalpanīyam ca saṅkalpayate, one thinks both good and bad thoughts; pāpmanā hi etat viddham, because the mind is vitiated by evil [ignorance],

Commentary:

Prāṇa is another name for Brahman. Prāṇa is pure, but when it is associated with the sense organs it is not pure. Similarly, Brahman as Brahman is pure, but with adjuncts it is not pure. It is not pure in the sense that it is subject to change.

Here, these adjuncts are referred to as pāpma, impure or evil, because they are limitations imposed on Brahman. These limitations are not real, however, but only apparent.

When the Upaniṣad speaks of the organs, it means the organs with their presiding deities. Both are described as pāpma. In these verses, some of the organs are mentioned, but it is to be understood that what is stated here about some organs applies to all the organs and their presiding deities.