Taittiriya Upanishad 2.5.1

2.5.1

vijñānaṃ yajñaṃ tanute /
karmāṇi tanute 'pi ca /
vijñānaṃ devāḥ sarve /
brahma jyeṣṭhamupāsate /
vijñānaṃ brahma cedveda /
tasmaccenna pramādyati /
śarīre pāpmano hitvā /
sarvānkāmānsamaśnuta iti /
tasyaiṣa eva śārīra ātmā /
yaḥ pūrvasya /
tasmādvā etasmādvijñānamayāt /
anyo 'ntara ātmā ' 'nandamayaḥ /
tenaiṣa pūrṇaḥ /
sa vā eṣa puruṣavidha eva /
tasya puruṣavidhatām /
anvayaṃ puruṣavidhaḥ /
tasya priyameva śiraḥ /
modo dakṣiṇaḥ pakṣaḥ /
pramoda uttaraḥ pakṣaḥ /
ānanda ātmā /
brahma pucchaṃ pratiṣṭhā /
tadapyeṣa śloko bhavati // 1//
iti pañcamo 'nuvākaḥ //

Knowledge actualises a sacrifice, and it executes the duties as well. All the gods meditate on the first-born Brahman, conditioned by knowledge. If one knows the knowledge-Brahman, and if one does not err about it, one abandons all sins in the body and fully enjoys all enjoyable things.

Of that preceding (mental) one this (cognitive) one is verily the embodied self. As compared with this cognitive body, there is another internal self constituted by bliss. By that one is this one filled up. This one, as aforesaid, has verily a human shape. It is humanly shaped in accordance with the human shape of the earlier one. Of him joy is verily the head, enjoyment is the right side, hilarity is the left side; Bliss is the self (trunk). Brahman is the tail that stabilises. Apropos of this here is a verse: