Valmiki Ramayana Aranya Kanda Sarga 53 Shloka 21

निर्घृणः pitiless, त्वम् you, महात्मनः of the noble, तस्य his, ईदृशम् such, अलीकम् deceiving, कृत्वा after doing, विषम् poison, पीत्वेव as if after drinking, चिरम् for long, धरितुम् to survive, न शक्ष्यसि not possible.

You are pitiless. You will not be able to survive for long after deceiving such noble Rama just as man cannot survive after drinking poison.