All prohibit the above substitution of svarita, except the ācāryāḥ - gārgya, kāśyapa and gālva; when an udātta or a svarita follows.,
This debars the preceding rule. That anudatta which is followed by an Udatta is उदात्तोदयः or उदात्तपरः ॥ The word उदय means पर in the terminology of ancient Grammarians. That anudatta which is followed by a svarita is called स्वरितोदयः ॥ These are Bahuvrihi compounds. Thus उदात्तोदयः — गा꣡र्ग्यस्त꣡त्र॑, वा꣡त्स्य॒॒ स्त꣡त्र॑ ॥ The word त꣡त्र is first acute by लित् accent, before this udatta, the य of these words does not become svarita. So with स्वरितोदयः — गा꣡र्ग्यः॒॒॑ क्व॑ वा꣡त्स्यः॒॒॑ क्व॑ ॥ The word क्व is svarita being formed by the तित् affix अत् 5.3.12; before this svarita the preceding य does not become svarita.
Why do we say, \except in the opinion of Gargya, Kasyapa and Galava\? Observe गार्ग्यः॑ क्व॑, गा꣡र्ग्य॑स्तत्र ॥ According to their opinion, the svarita change does take place.
The employment of the longer word उदय instead of the shorter word पर is for the sake of auspiciousness, for the Book has approached the end. The very utterance of the word उदय is auspicious. All sacred works commence with an auspicious word, have an auspicious word in the middle, and end with an auspicious word. Thus Panini commences his sutra with the auspicious word वृद्धि 'increase' in Sutra 1.1.1: has the word शिव 'the well-wisher' in the middle 4.4.143, and उदय at the end.
The mention of the names of those several Acharyas is for the sake of showing respect (pujartham).,