Valmiki Ramayana Bala Kanda Sarga 14 Shloka 30
Original Shlokaपशूनां त्रिशतं तत्र यूपेषु नियतं तदा। अश्वरत्नोत्तमं तस्य राज्ञो दशरथस्य च ।।1.14.30।।
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तदा then, तत्र there, पशूनाम् of animals, त्रिशतम् three hundred, तस्य राज्ञ: that king's, अश्वरत्नोत्तमम् the excellent of the horses from the stables, यूपेषु to the sacrificial posts, नियतम् was bound.
Three hundred animals and the jewel of the horses (from the stables) belonging to king Dasaratha were bound to the sacrificial posts.