Valmiki Ramayana Ayodhya Kanda Sarga 51 Shloka 11
Original Shlokaयो मन्त्रतपसा लब्धो विविधैश्च पराश्रमैः। एको दशरथस्येष्टः पुत्रः सदृशलक्षणः।।2.51.11।। अस्मिन् प्रव्राजिते राजा न चिरं वर्तयिष्यति। विधवा मेदिनी नूनं क्षिप्रमेव भविष्यति।।2.51.12।।
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यः whoever, दशरथस्य Dasaratha's, सदृशलक्षणः similar traits, एकः only, इष्टः favourite one, मन्त्रतपसा with austerities accompanied by mantras, विविधैश्च various, पराश्रमैः with much efforts, लब्धः obtained, पुत्रः son, अस्मिन् this (Rama), प्रव्राजिते is banished, राजा king, चिरम् for long, न वर्तयिष्यति not live, नूनम् certainly, मदिनां earth क्षिप्रमिव quickly, विधवा widow, भविष्यति will become.
This favourite son of Dasaratha who has similar traits like his father was born after he rigorously practised austerities accompanied by (Vedic) mantras. When he is banished, the king will not live long. Surely this land will soon be widowed.