Valmiki Ramayana Yuddha Kanda Sarga 114 Shloka 8
Original Shlokaन चैतत्कर्मरामस्यश्रद्धधामिचमूमुखे । सर्वतस्समुपेतस्यतवतेनाभिमर्षणम् ।।6.114.8।।
1 source checked for this shloka
चमूमुखे army, रामस्य of Rama, एतत् such, कर्म action, न श्रद्धधामि not action, सर्वतः always, समुपेतस्य fully equipped, तव your, तेन therefore, धर्षणम् fight
"You are always well equipped with the army, so such action (killing you) is not possible for Rama."