Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 31: Viśvāmitra, Rāma and Lakṣmaṇa Depart for Mithilā
Text 1.31.9

नास्य देवा न गन्धर्वा नासुरा न च राक्षसाः।
कर्तुमारोपणं शक्ता न कथञ्चन मानुषाः॥

nāsya devā na gandharvā nāsurā na ca rākṣasāḥ
kartum
āropaṇaṁ śaktā na kathañcana mānuṣāḥ

na = none; asya = that bow; devāḥ na gandharvāḥ na asurāḥ na ca rākṣasāḥ = of the devas, gandharvas, asuras, rākṣasas or; kartum = of; āropaṇam = stringing; śaktāḥ na kathañcana = have been capable; mānuṣāḥ = or human beings.

None of the devas, gandharvas, asuras, rākṣasas or human beings have been capable of stringing that bow.