CC Antya 8.66

yathā-yogya udara bhare, nā kare ‘viṣaya’ bhoga
sannyāsīra tabe siddha haya jñāna-yoga
Synonyms: 
yathā-yogya — as much as necessary; udara bhare — fills the belly; kare — does not do; viṣaya bhoga — material enjoyment; sannyāsīra — of a sannyāsī; tabe — then; siddha — perfect; haya — is; jñāna-yoga — spiritual advancement in knowledge.
Translation: 
“A sannyāsī eats as much as necessary to maintain his body, but he does not enjoy satisfying his senses materially. Thus a sannyāsī becomes perfect in his spiritual advancement in knowledge.