Valmiki Ramayana Bala Kanda Sarga 61 Shloka 18
Original Shlokaअविक्रेयं सुतं ज्येष्ठं भगवानाह भार्गव:।।1.61.17।। ममापि दयितं विद्धि कनिष्ठं शुनकं नृप। तस्मात्कनीयसं पुत्रं न दास्ये तव पार्थिव ।।1.61.18।।
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भगवान् venerable, भार्गव: descendent of Bhrugu, sage Richika, ज्येष्ठम् eldest, सुतम् son, अविक्रेयम् cannot be sold, आह is telling, नृप O King, शुनकम् named Sunaka, कनिष्ठम् youngest, मम for me, दयितम् beloved son, विद्धि you may better know, पार्द्धिव O King, तस्मात् for that reason, कनीयसं पुत्रम् yougest son, तव to you, न दास्ये I will not give.
Venerable descendant of the Bhrugus (sage Richika) said that the eldest son cannot be sold. "O King the youngest son, Sunaka, is my beloved son. You know, O King for that reason I will not give my yougest son".