Valmiki Ramayana Kishkindha Kanda Sarga 40 Shloka 36

तत्र there, दीर्घकालम् for a long time, बुभुक्षिताः very hungry people, महाकायाः those of huge body, असुराः demons, ब्रह्मणा by Brahma, समनुज्ञाताः have been permitted, नित्यम् ever, छायाम् shadow, गृह्णन्ति will be catching.

'Demons of huge bodies catch the shadows of passersby in that place as they have been hungry for long and have the permission of Brahma to do so.