Valmiki Ramayana Sundara Kanda Sarga 54 Shloka 28
Original Shlokaनाग्निस्तृप्यति काष्ठानां तृणानां च यथा तथा। हनूमान् राक्षसेन्दाणां विशस्तानां न तृप्यति।।5.54.28।।
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अग्निः fire, काष्ठानाम् with dry logs, तृणानाम् blades of grass, न तृप्यति is not satisfied, राक्षसेन्द्राणाम् of demon kings, विशस्तानाम् dead ones, न तृप्यति is not satisfied.
Just as fire is not satisfied with dry sticks and grass Hanuman was not satisfied with the dead demons.