Valmiki Ramayana Ayodhya Kanda Sarga 28 Shloka 23
Original Shlokaकायक्लेशाश्च बहवो भयानि विविधानि च। अरण्यवासे वसतो दुःखमेव ततो वनम्।।2.28.23।।
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अरण्यवासे living in the forest, वसतः while living, बहवः many, कायक्लेशाः physical afflictions, विविधानि various, भयानि च fears, ततः therefore, वनम् forest, दुःखमेव is full of difficulties only.
There are various physical afflictions and fears for one who lives in the forest. Therefore, forest brings suffering.