Valmiki Ramayana Yuddha Kanda Sarga 14 Shloka 20

सुवारिणा: into the pit, राघवसागरेण: ocean called Raghava, तरसा: to be destroyed, प्रच्छाद्यमानः engulfed, काकुत्स्थ: Kakutstha's, पातालमुखे: the underworld, पतन् fall into, अयम् us, भवद्भि: at present, समेत्य: joined together, तारयितुम् will have to make him free, युक्तः proper for you.

"He is going to fall into the ocean called Rama to be destroyed, engulfed in the pit of the shape of Kakutstha Rama, the underworld. It is proper for all of us to join and make him free."