श्येनतिलस्य पाते ञे

Operational rule vidhi

मुम् is the augment of the words श्येन and तिल before पात when the affix ञ् follows.

Word by word (padaccheda)

Target श्येनतिलस्य ṣaṣṭhī · ekavacanaRight context पाते saptamī · ekavacanaRight context ञे saptamī · ekavacana

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").

Full reading

श्येनतिलस्य पाते ञे

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

Commentary

मुम् is the augment of the words श्येन and तिल before पात when the affix ञ् follows.
Thus श्येनपातोऽस्यां क्रीडायां = श्येनंपाता, तैलंपाता ॥ See 4.2.58. Why do we say before ञ? Observe श्येनपातः ॥

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