Ramayana 1.21.18

तानि चास्त्राणि वेत्त्येष यथावत्कुशिकात्मज:।अपूर्वाणां च जनने शक्तो भूयस्स धर्मवित्।।।।

tāni cāstrāṇi vetty eṣa yathāvat kuśikātmajaḥ | apūrvāṇāṃ ca janane śakto bhūyaḥ sa dharmavit ||

This son of Kuśika knows those weapons in full and proper detail; and, being a knower of dharma, he is moreover capable of bringing forth even new, unprecedented weapons.