हिंसायां प्रतेश्च

Operational rule vidhi

The augment सुट् is placed before क , when the verb कृ comes after उप and प्रति and the sense 'to cause suffering'.

Word by word (padaccheda)

Right context हिंसायाम् saptamī · ekavacanaLeft context प्रतेः pañcamī · ekavacanaIndeclinable च avyaya

Right context Saptamī (7th case): "when X follows", the operation applies to what precedes (1.1.66 तस्मिन्निति निर्दिष्टे पूर्वस्य). Also a condition or domain ("in the sense of").
Left context Pañcamī (5th case): "after X", the operation applies to what follows (1.1.67 तस्मादित्युत्तरस्य). Also used for limits and sources.
Indeclinable An avyaya such as च "and", वा "optionally", न "not".

Full reading

हिंसायाम् प्रतेः च

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

Commentary

The augment सुट् is placed before क , when the verb कृ comes after उप and प्रति and the sense 'to cause suffering'.
Thus उपस्कीर्णम् or प्रतिस्कीर्णं हन्त ते वृषल भूयात् = तथा ते वृषल विक्षपो भूयाद् यथा हिंसामनुबध्नाति ॥

Why do we say when 'the sense is to cause pain'? Observe प्रतिकीर्णम् ॥

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