Four Upanisadic Mahâvâkyas and their Vedic settings

type of priest:invoking priestshandling priestssinging priests(nonliturgical)
hymn collection:Rk SamhitâYajuh SamhitâSâma SamhitâAtharva Samhitâ
ritual treatise:Aitareya BrâhmanaSatapatha BrâhmanaChândogya Brâhmana  …
philosophical treatise:Aitareya UpanisadBrhadâranyaka Upan.Chândogya Upan.Mândûkya Upanisad
mahâvâkya:Ait.Up. 3.3:Brh.Up. 1.4.10:Ch.Up. 6.8.7:Mand.Up. 2:
(Sanskrit text:)prajñânam brahmaaham brahmâsmitat tvam asiayam âtmâ brahma
(English translation:)“Consciousness is Brahman.”“I am brahman.”“That you are.”Brahman is this self.”

[Note: Each Veda has multiple branches, each of which may have it own Brahmana, Upanisads, etc. This table gives only one line among several for each of them.]