2.3.43
साधुनिपुणाभ्यामर्चायां सप्तम्यप्रतेः
Operational rule vidhi
In conjunction with the words साधु 'good' and निपुण 'skilful' when they denote respect, the 7th case-affix is used, provided that the word प्रति is not used.
Word by word (padaccheda)
With / by साधु- निपुणाभ्याम् tṛtīyā · dvivacanaRight context अर्चायाम् saptamī · ekavacanaSubstitute / term सप्तमी prathamā · ekavacanaTarget अप्रतेः ṣaṣṭhī · ekavacana
- With / by Tṛtīyā (3rd case): accompaniment or means.
- 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").
- Substitute / term Prathamā (1st case): in operational rules, the substitute or the thing introduced; in definitions, the term or its referent.
- Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
Full reading
साधु-
Pāṇini leaves out words that carry over from earlier sūtras. Expand to see the rule as a reader actually understands it.
अप्रतेः → सप्तमी / अर्चायाम्
Replace aprateḥ with saptamī when arcāyām follows. Inherited words (anuvṛtti) may add further conditions.
Commentary
In conjunction with the words साधु 'good' and निपुण 'skilful' when they denote respect, the 7th case-affix is used, provided that the word प्रति is not used.
मातरि साधुः or निपुणः 'good behaved towards his mother'? But साधुर्देवदत्तो मातरं प्रति 'Devadatta is good behaved towards his mother.'
Why do we say 'when respect is denoted'? Observe, साधुर्भृत्योराज्ञः 'the servant is good towards the king.' Here it is a bare statement of a fact.
The exception applies not only to प्रति but to other prepositions, like परि, अनु &c., as, मातरं परि साधुर्देवदत्तः ॥
Śrīśa Chandra Vasu, The Ashtadhyayi of Panini (1897), via ashtadhyayi.com.