Valmiki Ramayana Yuddha Kanda Sarga 114 Shloka 10

यदैव by that action, हनुमान् Hanuman, सुरैरपि even Suras, दुष्प्रवेशाम् difficult to enter, लङ्कांनगरीम् Lanka city, वीर्यात् valour, प्रविष्टः increasing, तदैव like that, वयम् knowing this, व्यथिताः worried

"To Lanka, which is inaccessible to anyone, Hanuman entered by increasing his valour. Knowing this we worried (that Rama may not be mere mortal)."