Valmiki Ramayana Sundara Kanda Sarga 1 Shloka 192
Original Shlokaस तस्या विवृते वक्त्रे वज्रसंहननः कपिः। संक्षिप्य मुहुरात्मानं निष्पपात महाबलः।।5.1.192।।
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महाबलः strong one, वज्रसंहननः of thunderboltlike physique, सः कपिः that vanara, आत्मानम् himself, मुहुः once again, संक्षिप्य contracted, तस्याः her, विवृते open, वक्त्रे in the mouth, निष्पपात entered.
Hanuman, the vanara whose physique was as hard as thunderbolt suddenly contracted once again and entered her opened mouth.