Saintly persons become powerful by execution of austerities. Their consciousness is unshakable because they do not try to enjoy anything within the material world. Such naturally liberated sages accept foodstuffs that are offered to them by destiny, and if by chance they happen to eat contaminated food, they are not affected, just like fire, which burns up contaminated substances that are offered to it.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
तेजस्वी तपसा दीप्तो दुर्धर्षोदरभाजनः । सर्वभक्षोऽपि युक्तात्मा नादत्ते मलमग्निवत्
tejasvī tapasā dīpto durdharṣodarabhājanaḥ | sarvabhakṣo'pi yuktātmā nādatte malamagnivat
SB 11.7.45