I am trying to find Buddha's word about Five Niyamas in Sutta. Or does it exist only in commentaries?
They are not the Buddha's words, I don't think. They are enumerated and defined in the Dhammasaṅgaṇī-aṭṭhakathā (Cittuppādakaṇḍo, Abyākatapadaṃ, Ahetukakusalavipāko, Vipākuddhārakathā):
Imasmiṃ pana ṭhāne pañcavidhaṃ niyāmaṃ nāma gaṇhiṃsu – bījaniyāmaṃ utuniyāmaṃ kammaniyāmaṃ dhammaniyāmaṃ cittaniyāmanti. Tattha kulatthagacchassa uttaraggabhāvo, dakkhiṇavalliyā dakkhiṇato rukkhapariharaṇaṃ, sūriyāvaṭṭapupphānaṃ sūriyābhimukhabhāvo, māluvalatāya rukkhābhimukhagamanameva, nāḷikerassa matthake chiddasabbhāvoti tesaṃ tesaṃ bījānaṃ taṃtaṃsadisaphaladānaṃ bījaniyāmo nāma. Tasmiṃ tasmiṃ samaye tesaṃ tesaṃ rukkhānaṃ ekappahāreneva pupphaphalapallavaggahaṇaṃ utuniyāmo nāma. Tihetukakammaṃ tihetukaduhetukāhetukavipākaṃ deti. Duhetukakammaṃ duhetukāhetukavipākaṃ deti, tihetukaṃ na detīti, evaṃ tassa tassa kammassa taṃtaṃsadisavipākadānameva kammaniyāmo nāma.
Bodhisattānaṃ pana paṭisandhiggahaṇe, mātukucchito nikkhamane, abhisambodhiyaṃ tathāgatassa dhammacakkappavattane, āyusaṅkhārassa ossajjane, parinibbāne ca dasasahassacakkavāḷakampanaṃ dhammaniyāmo nāma.
Ārammaṇena pana pasāde ghaṭṭite ‘tvaṃ āvajjanaṃ nāma hohi…pe… tvaṃ javanaṃ nāma hohī’ti koci kattā vā kāretā vā natthi, attano attano pana dhammatāya eva ārammaṇena pasādassa ghaṭṭitakālato paṭṭhāya kiriyamanodhātucittaṃ bhavaṅgaṃ āvaṭṭeti, cakkhuviññāṇaṃ dassanakiccaṃ sādheti, vipākamanodhātu sampaṭicchanakiccaṃ sādheti, vipākamanoviññāṇadhātu santīraṇakiccaṃ sādheti, kiriyamanoviññāṇadhātu voṭṭhabbanakiccaṃ sādheti, javanaṃ ārammaṇarasaṃ anubhavatīti ayaṃ cittaniyāmo nāma. Ayaṃ idha adhippeto.
According to Wiki article on niyamas these were written 5 to 18 CE. This is way after the Buddha's death. Also, according to wiki article, these are only commentaries. The article mentions which specific texts mentions them. They are quite a few.
This article seems to refer to the niyamas as something the buddha said:
As the other's have said the pañcavidha niyāma or "five-fold inevitability" is a commentarial way of talking about dependent arising. That said the idea of a limitation (niyāma) is found in many places in the Pāḷi Canon and was also taken up by the Yoga tradition. The term often occurs alongside the term dhammatā 'natural' in relation to paṭiccasamuppāda - experiences that arise in dependence on conditions are dhammatā.
In 2012, I located all the Pāḷi texts which use this list and translated them. At present the draft is free and on my website: Source Texts for the Five-fold Niyāma (pañcavidhaṃ niyāma). This document also includes mentions of dhammatā and niyāma in suttas. I hope to turn this material into a book at some stage.
There are two layers of commentary. Buddhaghosa, writing in about the 5th Century of the Common Era, and others writing in about the 13th Century, which was a very active time in Burma. Buddhaghosa is clearly most concerned with explaining karma in terms of bījaniyāma and utuniyāma, i.e. he uses analogies drawn from nature to explain why the effects of actions are appropriate and timely. The later Burmese commentators were more concerned with explaining how the cittavīthi or process of mental activity (aka cittaniyāma) worked using the same analogy.
My friend and Colleague Dhīvan (aka Dr Thomas Jones) has written about the modern history of the idea. It seems that Ledi Sayadaw and C. A. F. Rhys Davids reinterpreted the fivefold niyāma as "the five niyāmas" and made them into different "orders of conditionality". A theme that was taken up by Sangharakshita, the founder of the Triratna Buddhist Order. However this new formulation has almost nothing in common with the Pāḷi texts. Dhīvan's article for the Journal of Buddhist Ethics is The Five Niyāmas as Laws of Nature: an Assessment of Modern Western Interpretations of Theravāda Buddhist Doctrine. Dhivan has also written a more accessible account of the niyāmas on his blog: The ‘Five Niyamas’ and Natural Order.
I have also written some short essays about the term in other Indian darśanas, e.g.
- Niyama in the Sāṅkhyakārikā and Buddhaghosa's Commentaries
- Dharma-niyama in the Vyākaraṇa-Mahābhāṣya.