Valmiki Ramayana Sundara Kanda Sarga 13 Shloka 32
Original Shlokaभर्तृजेन तु दुःखेन ह्यभिभूता वनौकसः।।5.13.32।। शिरांस्यभिहनिष्यन्ति तलैर्मुष्टिभिरेव च।
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नौकसः vanaras, भर्तृजेन on account of the events affecting their king, दुःखेन by grief, अभिभूताः overpowered, तलैः with their palms, मुष्टिभिरेव च and with their fists, शिरांसि their heads, अभिहनिष्यन्ति will hit themselves.
"The grief due to the death of their king will make the vanaras hit their heads with their palms and fists.