SB 11.18.2

kanda-mūla-phalair vanyair
 medhyair vṛttiṁ prakalpayet
vasīta valkalaṁ vāsas
 tṛṇa-parṇājināni vā
kanda — with bulbs; mūla — roots; phalaiḥ — and fruits; vanyaiḥ — growing in the forest; medhyaiḥ — pure; vṛttim — sustenance; prakalpayet — one should arrange; vasīta — one should put on; valkalam — tree bark; vāsaḥ — as clothes; tṛṇa — grass; parṇa — leaves; ajināni — animal skins; — or.
Having adopted the vānaprastha order of life, one should arrange one’s sustenance by eating uncontaminated bulbs, roots and fruits that grow in the forest. One may dress oneself with tree bark, grass, leaves or animal skins.

A renounced sage in the forest does not kill animals, but rather acquires skins from animals who have suffered natural death. According to a passage from Manu-saṁhitā, quoted by Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura, the word medhyaiḥ, or “pure,” indicates that while residing in the forest a sage may not accept honey-based liquors, animal flesh, fungus, mushrooms, horseradish or any hallucinogenic or intoxicating herbs, even those taken as so-called medicine.