Valmiki Ramayana · Sundara Kanda · Sarga 1
प्लवङ्गप्रवरैर्दृष्टः प्लवने कृतनिश्चयः। ववृधे रामवृद्ध्यर्थं समुद्र इव पर्वसु
plavaṅgapravarairdṛṣṭaḥ plavane kṛtaniścayaḥ| vavṛdhe rāmavṛddhyarthaṃ samudra iva parvasu
Having made up his mind to leap for the cause of Rama, Hanuman began to grow in size just as the sea grows during the fullmoon and newmoon days, while the monkey troops were watching.
— M.N. Dutt (1891)
Commentary
Hanuman's growth is likened to the sea swelling at full moon — a beautiful natural simile. The phrase 'for the cause of Rama' (rāmavṛddhyartha) is key: his transformation is not for his own glory but in service of another. The watching monkey troops serve as witnesses to this extraordinary moment.
प्लवङ्गरामवृद्ध्यर्थपर्वसु