Valmiki Ramayana Bala Kanda Sarga 4 Shloka 6
Original Shlokaस तु मेधाविनौ दृष्ट्वा वेदेषु परिनिष्ठितौ। वेदोपबृंहणार्थाय तावग्राहयत प्रभु:।।1.4.6।।
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प्रभु: the master, स: that (Valmiki), मेधाविनौ endowed with intellect, वेदेषु in the knowledge of vedas, परिनिष्ठितौ accomplished, दृष्ट्वा having seen, वेदोपबृंहणार्थाय for the purpose of nourishing the vedas, तौ both of them, अग्राहयत got them initiated.
Valmiki, the master, having found both Kusa and Lava endowed with intellect and accomplished in the Vedas initiated them into the Ramayana composed by him for the purpose of nourishing the Vedas.