In the very beginning of Mahābhārata (Mahabharata), we hear the utterance of ‘Ṛta’ (Rita) from the lips of Ugraśravā (Ugrasrava) Sauti almost as a blessed utterance–

Ṛtam ekākṣaraṁ Brahma vyāktāvyāktaṁ sanātanam.

Here the term ṛta (rita) has been inseparably identified with the unspeakable Parabrahman, so it is also identified with the concept of Vyāktāvyakta Puruṣa (Purusha)and Ptakṛti (Prakriti) in Sāṁkhya (Samkhya) philosophy. It is evident that in Mahābhārata (Mahabharata), the term Ṛta (Rita) denotes an absolute entity. Perhaps for this very reason , ṛta (rita) is hailed as the Soul of God Nārāyaṇa (Narayana) — ṛtaṁ nārāyaṇātmakam.

It can be noticed that Ṛta (Rita) and Satya (Truth) are almost synonymised later. Even this trend can be marked in the Mahābhārata (Mahabharata). But in most of the cases, Ṛta (Rita) and Satya are mentioned separately. They are established in equal terms with Parabrahma in the Mahābhārata (Mahabharata) and in Purāṇas (Puranas). It was said that this Ṛta (Rita) was known by the Vedic sages as the Satya (Truth) and Brahma. In the same way, Ṛta (Rita) and Satya (Truth) are separately connected with the essence of the Vedic Puruṣasūkta (Purushasukta) in the Mahābhārata (Mahabharata)-

Idaṁ puruṣasūkta hi sarvavedeṣu pārthiva.
Ṛtaṁ satyaṁ c vikhyātaṁ ṛṣisiṁhena pārthiva.

The word, Ṛta (Rita) was first mentioned in the Ṛgveda (Rigveda). At first, the word Ṛta (Rita) was used to indicate the order of the earthly and divine discipline. As if, Ṛta (Rita) was an omnipotent divine controlling power. He was determining the rule of the deities like Mitra and Varuṇa (Varuna). The Earth and Nature were controlled by his rules-
Ṛtena viśvaṁ bhuvanaṁ virājathaḥ.

Then, the word, Ṛta (Rita) was used as a verb in the famous mantra or chant ‘Madhu vātā ṛtāyate’. It implied that the Ṛta (Rita) was shaping the way the wind was carrying honey, the mode in which the rivers offered honey-like water and how the earthly locales became beautiful.

This omnipotent influence of Ṛta (Rita) made him divine in the Vedas. It was said in a mantra or chant of the Ṛgveda (Rigveda)- Ṛta (Rita) was voluminous. He was also represented as someone who could carry the world and who had a pleasant personality. The praising Vaidikas asked for more rice from Ṛta (Rita). The cows entered the Dakṣiṇā or the southern land by the help of Ṛta (Rita). The whole of heaven and earth is under the control of Ṛta (Rita), that dyāvāpṛthivī (dyavaprithivi) gets milk issued out of the cow for the sake of Ṛta (Rita) —

ṛtāya pṛthvī vahule gabhīre/ ṛtāya dhenu parame duhate

In another mantra, this great Ṛta (Rita) is mentioned alongside Devamātā (Devamata) Aditi, Dyāvāpṛthivī (Dyavaprithivi),, Indra, Viṣṇu (Vishnu) and the Marut gods. Thus, Ṛta (Rita) has been elevated to the level of divinity.

The word Ṛta (Rita) was used in a purely ethical sense in the Yama- Yamī (Yami) tale in the Ṛgveda (Rigveda). Yamī (Yami) asked Yama for a sexual relationship though they were siblings. But Yama resisted this effort vehemently. He said- ” We have not done this earlier. How can we indulge in it now? We have uttered Ṛta (Rita) before. How can we utter Anṛta (Anrita) now?” –
Ṛtā vadanto anṛtaṃ rapema.

Here Ṛta (Rita) symbolises Satya or Truth uttered in a truthful and ethical way. Anṛta (Anrita) symbolises uttering Asatya or false in an unethical way. Actually it should be said that Ṛta (Rita) and Satya are used simultaneously, in one line, but with different meanings. In a mantra or chant, it is represented that Ṛta (Rita) and Satya were born out of Tapas or prajvalita tapasyā (prajvalita tapasya or burning fire of sacrifice)-

Ṛtañca satyaṃ cābhīdvāt taposo’dhyajāyata.

This can be understood that the domain of Ṛta (Rita) was quite broad. Ṛta (Rita) incorporated all the religions and justice. Satya implies the symbolic place of truth and discipline. The negative word for Ṛta (Rita) was Anṛta (Anrita). This Anṛta (Anrita) signified the negative aspect of both Ṛta (Rita) and Satya. It was used in this sense in the tale of Yama- Yamī (Yami) in the Vedas. Śankarācārya (Sankaracharya) told- ‘Satyānṛte mithunīkṛtya’.

The simultaneous use of Ṛta (Rita) and Satya in one place ultimately makes us realise that Ṛta (Rita) and Satya are words belonging to the same line-
Ṛtaṃ vadannṛtadyumna satya vadan satyakarman.
It was proved again when Anṛta (Anrita), which was used as a negative expression of Ṛta (Rita), also implied the opposite of the word, Satya in the Ṛgveda (Rigveda). Satya and Anṛta (Anrita) were used together in a composite expression. Here the word, ‘Asatya’ was not used as a negative of ‘Satya’-
Satyānṛte avapaśyan jalānāṃ.

As Ṛta (Rita) and Satya were used alternately, the use of the word Ṛta (Rita) later decreased. Instead, Satya was used more prominently. But it must be noticed that even in this perspective, Ṛta (Rita) and Satya were used synonymously in the Upaniṣada (Upanishada).Even it was said in the Mahābhārata (Mahabharata) and in the Taittirīya Upaniṣada (Taittiriya Upanishada)-
Brahma vadiṣyāmi. Ṛtaṃ vadiṣyāmi. Satyaṃ vadiṣyāmi.

Or it was also said-

Ṛtañca sādhyāya-pravacane c.

And in the Mahābhārata (Mahabharata), it was said-
Ṛtaṃ satyaṃ hi vikhyātaṃ ṛṣisiṁhena pārthiva.