6.4.100 घसिभसोर्हलि च

Word by word (padaccheda)

Target घसि- भसोः ṣaṣṭhī · dvivacanaRight context saptamī · ekavacanaIndeclinable च avyaya

Target Ṣaṣṭhī (6th case): names what gets replaced, "in place of X" (1.1.49 षष्ठी स्थानेयोगा).
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").
Indeclinable An avyaya such as च "and", वा "optionally", न "not".

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

घसि-भसोः च

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

Commentary

The root-vowel of घस् and भस् is elided in the छन्दस् (Vedas) before any affix whether beginning with a vowel or a consonant which has an indicatory क् or ङ् ।
Thus सग्धिश्चमे सपीतिश्च मे, बब्धांते हरी धानाः ॥ सग्धिः is thus derived : क्तिन् is added to the root अद्; then by 2.4.39, घस् is substituted for अद्; thus घस् + ति = घस + ति (अ being elided by the present sutra) = घ् + ति (स् being elided by 8.2.26), then त is changed to ध, and घ to ग and we have ग्धिः ॥ Then समाना ग्धिः = सग्धिः (समान changed to स 6.3.84). The word बब्धाम् is the Imperative of भस्, thus भस् + श्लु + ताम् = भ भस् + ताम् स् = ब भ्स् + ताम् 6.4.100 = बभ् + ताम् 8.2.26 = ब ब् + धाम् बब्धाम् ॥ This rule of elision being a nitya and a subsequent rule ought to have operated first, but, as a Vedic anomaly, the reduplication takes place first. See 7.2.67

Why do we read "before an affix beginning also with a consonant"? Because the elision takes place before a vowel affix also, as बप्सति = भस् + श्लु + झि = ब भस् + अति 7.1.4 बप्सति 8.4.55.

Why having an indicatory क् or ङ्? Observe अंशून् बभस्ति ॥ The च has been added into the aphorism by the Vartikakara.

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