कस्येत्

Operational rule vidhi

In the meaning of 'सा अस्य देवता', the word 'क' gets the 'इत्' आदेश.

Word by word (padaccheda)

Target कस्य ṣaṣṭhī · ekavacanaSubstitute / term prathamā · ekavacana

Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.

Dotted words are technical terms. Hover or tap one to see its card.

Full reading

कस्य

Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.

As a rewrite rule (sketch from case endings)

कस्य →

Replace kasya with it. Inherited words (anuvṛtti) may add further conditions.

Commentary

The short इ is the substitute of the final अ of क when the affix is added.
Thus क + अण् = कि + अण् = कै + अ = कायं "oblation sacred to Ka". As कायं हविः, कायमेककपालं निर्वपेत् ॥

Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.