3.2.13 स्तम्बकर्णयो रमिजपोः

Word by word (padaccheda)

Right context स्तम्ब- कर्णयोः saptamī · dvivacanaTarget रमि- जपोः ṣaṣṭhī · dvivacana

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").
Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).

Dotted words are technical terms, dashed ones pratyāhāras (names for classes of sounds or affixes). Hover or tap one to see its card.

Full reading

स्तम्ब-कर्णयोः रमि-जपोः

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

Commentary

The affix अच् comes after the verb रम् 'to sport' and जप् 'to whisper' when the case-inflected words स्तम्भ 'a clump of grass' and कर्ण 'ear' are in composition with them respectively.
The verb रम् is intransitive and the verb जप् can take an object under very limited circumstances, only namely when the object denotes Sabda ; therefore in the case of both these verbs, the object cannot be in composition as an accusative case; therefore, the upapada here must be a general case-inflected word. Hence we have read the anuvritti of the word सुप् from sutra 4 into this, the anuvritti of the word कर्म्म being inapplicable here.

Vart:- The words to be formed must have the sense of 'elephant' and a 'tale-bearer'. Thus स्तम्बेरमते = स्तम्बेरमः 'an elephant (lit. who sports in cluster of grass)' कर्णे जपति = कर्णेजपः 'a slanderer (lit. who whispers in the ear)'.

The affix अच् is not employed when the words to be formed do not mean an 'elephant' and a 'traducer'. Thus स्तम्बे रन्ता 'who plays in clusters of grass'. कर्णे जपिता मशकः 'the mosquito that hums near the ear'.

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