Valmiki Ramayana Kishkindha Kanda Sarga 15 Shloka 21
Original Shlokaतत्क्षमं न विरोधस्ते सह तेन महात्मना। दुर्जयेनाप्रमेयेन रामेण रणकर्मसु4.15.21।।
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तत् therefore, महात्मना great, रणकर्मसु in war, दुर्जयेन unconquerable, अप्रमेयेन of immeasurable, तेन रामेण by that Rama, ते to you, विरोधः enmity, न क्षमम् not desirable.
'Rama is immeasurable in prowess and unconquerable in war. Therefore, enmity with him is not desirable for you.