Valmiki Ramayana Ayodhya Kanda Sarga 72 Shloka 51
Original Shlokaतमपश्यन्प्रियंपुत्रं महीपालो महायशाः। पुत्रशोकपरिद्यूनः पञ्चत्वमुपपेदिवान्।।2.72.51।।
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महायशाः renowned, महीपालः ruler of this earth, तम् that, प्रियं पुत्रम् beloved son, अपश्यन् not being able to behold, पुत्रशोक परिद्यूनः stricken by filial grief, पञ्चत्वम् the state of merger in the five elements, उपपेदिवान् obtained.
The renowned ruler of the earth (king Dasaratha), unable to behold (the sorry state of) his beloved son and stricken by filial grief, merged into the five elements (died).