Valmiki Ramayana Aranya Kanda Sarga 43 Shloka 42
Original Shlokaसमुत्थाने व तद्रूपं कर्तुकामं समीक्ष्य तम्। उत्स्मयित्वा तु भगवान्वातापिमिदमब्रवीत्।।3.43.42।।
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समुत्थाने when he rose, तत् that, रूपम् form, कर्तुकामम् to turn into real form, तम् him, वातापिम् Vatapi, समीक्ष्य after seeing, भगवान् venerable sage, उत्स्मयित्वा by smiling at him, इदम् this, अब्रवीत् said.
When the venerable sage Agastya got up (after eating), he observed Vatapi wishing to turn into his real form. So smiling at him, he said: