Which Upanishad in the Yajur Veda references jñāna and ajñāna?

Question

I remember having read about the terms Jñāna and ajñāna (gyan and agyan) in an Upanishad from the Yajur Veda. I know what the terms mean, and I know that they are present in certain other texts, but I'm trying to find their definition according to the Yajur Veda specifically. I can't find it even when I look through the citations in the entries from Wisdom Lib linked above, but I am quite certain that I read about it. Any help?

Answer 1

Aha- I've found it. It was in the Niralamba Upanishad, which seems to be a minor Upanishad, formatted in a sort of 'Q&A' style. Quoting from the translated version linked above:

24: What is Jñāna?

It is the realisation by direct cognition of the fact that in this changing universe there is nothing but Caitanya [the one life] that is Consciousness, that is of the form of the seer and the seen, pervading all things, that is the same in all, and that is not subject to changes like pot, cloth, etc. This realisation is brought about by means of the subjugation of the body and the senses, the serving of a good Guru (teacher), the hearing of the exposition of Vedāntic doctrines and constant meditation thereon.

25: What is Ajñāna?

It is the illusory attribution, like the snake in the rope, of many Ātmās (souls) through the diverse Upādhis [or vehicles] of the angels, beasts, men, the fixed ones, females, males, castes and orders of life, bondage and emancipation, etc., to Brahman that is secondless, all-permeating and of the nature of all.

Answer 2

1. Shukla Yajurveda Brihadaranyaka Upanishad Verse 4.4.10 uses the terms vidyA and avidyA

अन्धं तमः प्रविशन्ति येऽविद्यामुपासते । ततो भूय इव ते तमो य उ विद्यायां रताः ॥ १० ॥

andhaṃ tamaḥ praviśanti ye'vidyāmupāsate | tato bhūya iva te tamo ya u vidyāyāṃ ratāḥ || 10 ||

10. Into blinding darkness (ignorance) enter those who worship ignorance (rites). Into greater darkness, as it were, than that enter those who are devoted to knowledge (the ceremonial portion of the Vedas).

Same verse is also present in Isavasya upanishad 9.

2. Krishna Yajurveda Katha Upanishad 1.2.4 also uses the terms vidyA and avidyA.

दूरमेते विपरीते विषूची अविद्या या च विद्येति ज्ञाता । विद्याभीप्सिनं नचिकेतसं मन्ये न त्वा कामा बहवोऽलोलुपन्त ॥ ४ ॥

dūramete viparīte viṣūcī avidyā yā ca vidyeti jñātā | vidyābhīpsinaṃ naciketasaṃ manye na tvā kāmā bahavo'lolupanta || 4 ||

4. These two are wide apart, mutually exclusive, leading to different ways, known as ignorance and knowledge. I regard Nachiketas as wishing for knowledge; desires, though numerous, have not shaken thee.

Addition

3. In Krishna Yajurveda Taittiriya Upanishad 2.6, the terms, vijnAnam and avijnAnam are used.

असन्नेव स भवति । असद्ब्रह्मेति वेद चेत् । अस्ति ब्रह्मेति चेद्वेद । सन्तमेनं ततो विदुरिति । तस्यैष एव शारीर आत्मा । यः पूर्वस्य । अथातोऽनुप्रश्नाः । उताविद्वानमुं लोकं प्रेत्य । कश्चन गच्छती आहो विद्वानमुं लोकं प्रेत्य । कश्चित्समश्नुता३ उ । सोऽकामयत । बहुस्यां प्रजायेयेति । स तपोऽतप्यत । स तपस्तप्त्वा । इदꣳसर्वमसृजत । यदिदं किञ्च । तत्सृष्ट्वा । तदेवानुप्राविशत् । तदनु प्रविश्य । सच्च त्यच्चाभवत् । निरुक्तं चानिरुक्तं च । निलयनं चानिलयनं च । विज्ञानं चाविज्ञानं च । सत्यं चानृतं च सत्यमभवत् । यदिदं किञ्च । तत्सत्यमित्याचक्षते । तदप्येष श्लोको भवति ॥ १॥ इति षष्ठोऽनुवाकः ॥

asanneva sa bhavati . asadbrahmeti veda cet . asti brahmeti cedveda . santamenaṃ tato viduriti . tasyaiṣa eva śārīra ātmā . yaḥ pūrvasya . athāto’nupraśnāḥ . utāvidvānamuṃ lokaṃ pretya . kaścana gacchatī āho vidvānamuṃ lokaṃ pretya . kaścitsamaśnutā3 u . so’kāmayata . bahusyāṃ prajāyeyeti . sa tapo’tapyata . sa tapastaptvā . idagͫsarvamasṛjata . yadidaṃ kiñca . tatsṛṣṭvā . tadevānuprāviśat . tadanu praviśya . sacca tyaccābhavat . niruktaṃ cāniruktaṃ ca . nilayanaṃ cānilayanaṃ ca . vijñānaṃ cāvijñānaṃ ca . satyaṃ cānṛtaṃ ca satyamabhavat . yadidaṃ kiñca . tatsatyamityācakṣate . tadapyeṣa śloko bhavati .. 1.. iti ṣaṣṭho’nuvākaḥ ..

If he knows Brahman as non-existent, he becomes himself non-existent. If he knows Brahman as existent, then (they) the world knows him to be existent. Of the former (Anandamaya kosha), the Self is the essence. Thereupon arise the following questions: Does the ignorant, leaving this world, go There? Or, does the knower, leaving this world, obtain That? He desired, ‘I shall become many and be born. He performed Tapas. having performed Tapas, He created all this (whatever we perceive). Having created it, He entered into it. Having entered it, He became the manifest and the unmanifest, the defined and undefined, the housed and the houseless, knowledge and ignorance, truth and falsehood, and all this whatsoever that exists. Therefore, it is called Existence. In this sense, there is the following Vedik verse.