Ramayana
श्रुत्वागस्त्येरितं वाक्यं रामो विस्मयमागतः । कथमासीत्तु लङ्कायां सम्भवो रक्षसां पुरा ॥ 7-4-1 ॥
Having heard the words uttered by Agastya, Rama was struck with wonder, wondering how the origin of the Rakshasas in Lanka had come about in former times.
english translation