Valmiki Ramayana Yuddha Kanda Sarga 113 Shloka 15

यः he who, देवतानाम् Devatas, तथा so also, दानवरक्षनाम् Danavas, Rakshasas, अवध्यः not be killed, सःअयम् he, पदातिना by walk, मानुषेण by a mortal, रणे in battle, हतः killed, शेते lies asleep

"He, whom Devatas, Danavas and Rakshasas could not kill, lies asleep, killed by a mortal who came by walk."