Valmiki Ramayana Kishkindha Kanda Sarga 46 Shloka 7
Original Shlokaअथाऽहं कृतबुद्धिस्तु सुव्यक्तं निहतो गुरुः। शिला पर्वतसङ्काशा बिलद्वारि मया कृता।।4.46.7।। अशक्नुव न्निष्क्रमितुं महिषो विनशेदिति।
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अथ then, गुरुः brother Vali, सुव्यक्तम् it is evident, निहतः killed, अहम् I, कृतबुद्धिः I thought, महिषः buffalo, निष्क्रमितुम् to return, अशक्नुवन् being unable, विनशेदिति should be destroyed, मया by myself, पर्वतसङ्काशा of the mountain size, शिला rock, बिलद्वारि at the entrance of, कृता placed.
'Thereafter, convinced that my brother was killed, I placed a mountainsize rock at the entrance of the cave so that Dundubhi will be destroyed, unable to come out of the cave.