Vedas have two broad classification in respect of Knowledge and Duties, Gnana Kanda and Karma Kanda.
These two are not segregated and appear throughout the Four Vedas.
One has to segregate the Karma Kanda from the Gnana Kanda, which consists of Hymns and the enquiry into the Nature of The Self, the Upanishads.
One has, in Hinduism two kinds of Duties.
One is Nithya Karma, Daily Duties that are to be performed regularly daily and another Naimithika Karma, Duties to be performed with a specific purpose and for specific occasions.
Today, we have all the Mantras and Rituals inan orderly fashion and we follow them.
The source, the Vedas are vast and the information is spread over.
How and who organised it?
Apasthamba organised it for those who live below the Geographical area Vindhya and Sathpura Range of Mountains.
But he had a pointer and for those in the Northern area of Vindhyas, there is a master file of Reference, which is not well known.
Curiously it is an Upanishad that deals with not only with the enquiry into Reality but to daily Routine and other Mantras for specific occasions.
The Mahanarayana Upanishad is in Krishna Yajur Veda.
It contains the daily duties , procedures, mantras, and Devatha Gayatris.
This Upanishad is also called Yagniki Upanishad as it deals at length with passages from Vedas and other Upanishads in parts or full used in religious acts of worship. According to Sage Sayana this Upanishad contains whatever mantras left over to be chanted in respect of Karma, Upaasana and Jnaana after the recital of Samhitha and Braahmana which are brought together in this rare compilation.
Gayatri mantras in Maha Narayana Upanishad.
We meditate upon the one who has beautiful colored wings for that purpose. May the Garuda invigorate us in our meditation to Purusha.
Krinushvapaaja iti pancha | Five mantras for destruction called Krinushvapaaja.
Krinushava-paajah prasitim na prithveem yaahi raajevam-avaagam ibhena |
Trishvirna-manu prasitim droonanoe-astaasi vidhya rakshasas-tapishthaih ||
Tava brhamaasa aasuyaa patanty-anu sprisa dhrishataa sosuchaanah |
Tapoo(goo)mshy-agne juhvaa patangaana-sandito visrija vishwa-gulkaah ||
Go forward in rapid flight whirling fiery torches. Burning with fury, follow them closely. Spread
The flying flames with your tongue. Cast around them your fireballs.
Pratispaso visrija toorni-taamo bhavaa paayur-viso asyaa adabdhah |
Yo no doore adhasa(ga)m so yo anty-agne maakishte vyathir-aada-dharsheet ||