Valmiki Ramayana Bala Kanda Sarga 38 Shloka 20
Original Shlokaस च ज्येष्ठो नरश्रेष्ठ सगरस्यात्मसम्भव:। बालान् गृहीत्वा तु जले सरय्वा रघुनन्दन।।1.38.20।। प्रक्षिप्य प्रहसन्नित्यं मज्जतस्तान् समीक्ष्य वै।
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नरश्रेष्ठ O Best among men, रघुनन्दन O Rama, ज्येष्ठ: eldest son, स: सगरस्य आत्मसम्भव: that Sagara's son Asamanjasa, नित्यम् every day, बालान् children, गृहीत्वा seizing hold of, सरय्वा: river Sarayu's, जले waters, प्रक्षिप्य throwing them, निमज्जत: while they were drowning, तान् them, समीक्ष्य beholding, प्रहसन् while laughing (rejoiced).
O best among men, delight of the Raghus (in the mean time) sagara's eldest son Asamanjasa, used to seize hold of children and throw them into the waters of river Sarayu. And while they were drowning, he was laughing.