Valmiki Ramayana Kishkindha Kanda Sarga 41 Shloka 17

ततः then, प्रसन्नेन by the pleasing one, महात्मना by the great soul, तेन by him, अनुज्ञाताः permitted, अथ then, ग्राहजुष्टाम् inhabited by alligators, ताम्रपर्णीम् Tamraparni, महानदीम् great river, तरिष्यथ cross.

'You will then come cross the great river Tamraparni infested with alligators. Cross it with the permission of the sage pleased (with you).