Valmiki Ramayana Ayodhya Kanda Sarga 82 Shloka 13
Original Shlokaज्येष्ठ श्श्रेष्ठश्च धर्मात्मा दिलीपनहुषोपमः। लब्धुमर्हति काकुत्स्थो राज्यं दशरथो यथा।।2.82.13।।
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ज्येष्ठः eldest, श्रेष्ठः च and also eminent, धर्मात्मा righteous one, दिलीपनहुषोपमः comparable to Dilipa and Nahusha, काकुत्स्थ Rama of Kakutstha dynasty, दशरथो यथा like Dasaratha, राज्यम् kingdom, लब्धुम् to inherit, अर्हति deserves.
The eldest, eminent and righteous Rama, the scion of the Kakutstha dynasty, who is comparable to Dilipa and Nahusha deserves to inherit this kingdom just as Dasaratha did.