What scriptures say that Prana Pratishtha is removed by a Chandala's touch?

Question

As I discuss in this question, by far the most popular school of Hindu philosophy is the Vedanta school. But there are five other Astika or orthodox schools of Hindu philosophy: Purva Mimamsa, Samkhya, Yoga, Vaisheshika, and Nyaya. My question is about the Nyaya and Vaisheshika schools. Udayana's Nyaya Kusumanjali is a 10th century Nyaya-Vaisheshika work which seeks to logically prove the existence of God. In this excerpt from the Nyaya Kusumanjali, Udayana tries to refutes the Purva Mimamsa belief that objects have Shaktis or inherent capacities to do things:

"[H]ow in images, etc., do such ceremonies become effectual as those for inviting to deity to take up residence therein, etc.? We hold therefore that we must admit such a thing as a capacity produced by the rite Pratishtha which can be destroyed by the touch of impure persons as the Chandala, etc., which renders an image a fit object of worship." ... The 'special causes' are the various kinds of merit in the person. The deities become conciliated in the ceremonies of consecration, and show it by coming to take up their residence, i.e. by the appropriation of the image and self-consciousness thereto; but by the touch of an impure person such appropriation and self-consciousness are rendered void.

For those who don't know, Prana Pratishtha is a ritual where you invoke the presence of a god into a statue. My question is, what scriptures say that the presence of a god in a statue is removed if it's touched by a Chandala?

Note that I don't want answers that comment on the nature of the caste system, untouchability, etc. I just want a specific answer on the Praha Pratishtha point.

Answer 1

Yes, it's likely to be true.
Short answer: ChAndAla-s are not allowed within the city limit, let alone the temples.
Note: We are talking about god's idol here and Not god. Refer the analogy for better interpretation.

Ancient Indian culture was highly relying on vibes and aura, based on which Certain things are auspicious & inauspicious.

ChAndAla & their social role

Refer this post: What are the order & duties of the children born from intermixing/hybridisation of 4 classes?

If a Sudra unites with a [Brahmana] woman belonging to the foremost of the four orders, the son that is begotten is called a Chandala. Endued with a fierce disposition, he must live in the outskirts of cities and towns and the duty assigned to him is that of the public executioner. Such sons are always regarded as wretches of their race. These, O foremost of intelligent persons, are the offspring of intermixed orders.

From above, it's clear that ChAndAla-s are usually outcasted from soceity (if not outlawed) & mostly they are not welcomed within the town limit itself.
If temple's idol is revered by several society people then certainly when a ChAndAla touches it, it's more likely to bring those inauspicious vibes he/she carries along. The idol may loose its original auspicious aura in front of devotees [once they know].

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Analogy

If one earns a degree from a reputed institute, then he/she may not want to give that certificate paper in a dirty/careless hands. The memento of that degree in form of certificate, means a lot for the achiever.
However, suppose if the certificate is lost or got dirty, even then the education earned by that person will remain intact.

A realised person (including the lord) doesn't differentiate among various subjects of society:

BG 5.18 - The learned ones look with equality on a Brahmana endowed with learning and humility, a cow, an elephant and even a dog as well as ChAndAla.

Answer 2

Well, nowhere its specifically mentioned that only chandala. Even a brahmin if touches idol without bathing and without following rules of brahmacharya, He too is considered chandala and the same thing applies. Chandala is not really caste, its behaviour or habits of a person which makes one chandala. and infact a brahmin doesn't even go into puja room in their home without taking bath and performing necessary rituals and without madi.

Prana prathishta is a very rigorous process to initiate energy in the idol, this energy is needed to be maintained so that the devotees who visit temple get benefitted by this positive energy. It's considered that in swayambhu temples the idols positive energy is limitless and in temples where pranaprathishta is done by great sages, it's little less, in temples where learned Veda pandits do prana prathishta, it's little lesser, in small temples where the prana prathista is done by a person who daily performs Sandhya Vandana and strictly follows his dharma, in those temples the energy gradually increases as the rituals are done daily, but that need to be protected for devotees benefit. Apart from this, there is another reason for it. if people are allowed to touch idols, then over the time the idol will go through corrosion and only pieces will remain. If you observe the poles in temple-like Tirumala, you can see those poles get so smooth over time and get very thin that they need to be replaced. Now imaging what happens to an idol if everyone is allowed to touch them? If you look at KABA where the black stone was open for people to touch, now there only remains pieces of stone , and they are struggling to protect it. But for Hindus, the idol needs to be protected for its shape and features carved or even its swayambhu.

All those abhishekas with milk and other panchamruthas are not superstition, its the process to protect idols from corrosion for thousands of years.

So it's more about protecting the energy stored in idol by daily rituals which are distributed to devotees during their visit to the temple. No one except the pradhanacharya is allowed into temple to touch idol, Not even a brahmana.

Only those who are responsible to take care of idols daily puja are allowed and they too should strictly follow the process. Should stick to shastras depending upon the temple. Majority of temples follow agama shastra, there might be few exceptions where the different process might be followed.

Its just misconception that only Chandalas were not allowed, no one is allowed in garbhalayam. Not even brahmin not even king. No one is greater than god and it is the responsibility of archaka who is appointed to keep the idol of god energized by daily following rituals and chanting mantras. So that devotees who come to visit god get benefitted by that positive energy.