Sama Veda · Talavakara Brahmana of the Sama Veda · 34 mantras
Kena Upanishad
Kenopaniṣad
Central theme: That by which the mind thinks — Brahman as the prior consciousness
Opens with the disciple's question: "By whom (kena) is the mind directed? By whose will does prana move? Who makes the eye see, the ear hear?" The answer: the Self is the Ear of the ear, the Mind of the mind — it cannot be known by what it makes known. The second half tells the story of the devas' pride after defeating the asuras; Brahman appears as a yaksha and humbles Agni, Vayu and Indra in turn.
Kena 1.5
यन्मनसा न मनुते येनाहुर्मनो मतम् । तदेव ब्रह्म त्वं विद्धि नेदं यदिदमुपासते
Yan-manasā na manute yenāhur mano matam, tadeva brahma tvaṁ viddhi nedaṁ yad-idamupāsate
That which the mind cannot think but by which the mind itself is thought — know that alone as Brahman, not what people worship as this.
The seer cannot be seen, the knower cannot be known — you are That.