Ancient rishis were married, was sanyasa invented by Buddhists and Jains?
Was sanyasa (renunciation of worldly life, monasticism) then a concept invented by the shramana movement including Buddhists and Jains, and later imported into Hinduism?
No, it has its origins in the Upanishads.
The view that Sannyasa and other celibate orders are non-Vedic has been held by ancient followers of the Vedas.
Maharishi Gautama says:
Gautama (3.35)—‘There is only one life-stage, say the revered Teachers; since the householder’s life is the only one that is directly enjoined [in the Vedas].’
Patrick Olivelle, an Indologist, says:
Since the celibate orders of life contradicts the Vedic injunction to marry and to procreate, Gautama and Bodhayana argue that scriptural passages authorizing such states are without authority.
This viewpoint is mentioned by the ancient Sri Vaishnava Acharya Yadava Prakasha, in his work called Yatidharma Samuccaya, or "Collection of the rules for Sannyasis," in which he says:
Some [the opponent of celibate orders] claim that there is indeed no such rule [of celibacy], because one is not found in the Veda, and because scriptures that contradict the Veda are without authority. That is the view of Gautama.
The opponents of the orders of celibacy say that the injunctions in the Vedas about meditation, knowledge, taking up the vow of asceticism, etc do not constitute a separate ashrama (order), but are done within the householder order itself. This is because they think that the Vedas only establish a single order, the householder, and any Smriti injunction that establishes celibate orders is non-Vedic. So, if there are Vedic injunctions that seem to suggest sannyasa, those injunctions are to be done within the householder order.
Yadava Prakasha then answers this objection:
To all this we reply. There is an exclusive observance known as the yoga of knowledge. The following Vedic text, accordingly, notes at the outset the rites beginning with "truth" and ending with "mental," (Mahanarayana Upanishad) goes on to prescribe renunciation: "They say that renunciation, therefore, surpasses these austerities," (Mahanarayana Upanishad) and finally enjoins the yoga of knowledge as what is expressed by the term renunciation: "One should attach oneself to the self." Now, the yoga of knowledge consists in the sole pursuit of knowledge. Such a pursuit, evidently, is not possible for householders, because they are required to perform in addition rites such as the daily fire sacrifice. Only the yoga of rites, consequently, is applicable to them. Now, the yoga of rites consists in the simultaneous pursuit of both knowledge and rites, from which pursuit its practitioners obtain liberation. Wandering ascetics, on the other hand, attain liberation solely through the yoga of knowledge. Because they do not perform rites, therefore, the same text in a subsequent passage shows how they accomplish the ritual and prescribes that a wandering ascetic should carry it out every day without fail: "In the case of a man who knows the sacrifice in this manner, [his self is the sacrificer, faith is his wife, his body is the fire wood...]." (Mahanarayana Upanishad) This is not merely a laudatory statement but a true injunction, because it has no precedent.
It is thus established that the yoga of knowledge pertains to wandering ascetics, while the yoga of rites pertains to householders. The Veda accordingly declares that a person can attain immortality only by abandoning rites: "Not by rites, not by offspring, and not by wealth - but by renunciation did some people attain immortality." (Mahanarayana Upanishad).
So no, sannyasa was not invented by the Buddhists and Jains.
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