छन्दसि वनसनरक्षिमथाम्

Operational rule vidhi

In the छन्दस् (Vedas) the affix इन् comes after the verbs वन् 'to honour', सन् 'to worship', रक्ष् 'to protect' and अथ् 'to agitate', when the object is in composition.

Word by word (padaccheda)

Right context छन्दसि saptamī · ekavacanaTarget वन- सन- रक्षि- मथाम् ṣaṣṭhī · bahuvacana

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

छन्दसि वन-सन-रक्षि-मथाम्

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

Commentary

In the छन्दस् (Vedas) the affix इन् comes after the verbs वन् 'to honour', सन् 'to worship', रक्ष् 'to protect' and अथ् 'to agitate', when the object is in composition.
Thus ब्रह्मवनिं त्वा क्षत्रवनिम् (Vaj. San. I.17., V. 12., VI.3); उत नो गोपतिं (Rig. Ved. (VI.53.10)) यै ते श्वानौ पथिरक्षो (Rig. Ved. (X. 14. II)) इन्द्रा यातूनामभवत् पाराशरो हविर्मथीनाम् (Rig. Ved. (VII.104.21)).

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