CC Madhya 12.53

prabhu kahe, — pūrṇa yaiche dugdhera kalasa
surā-bindu-pāte keha nā kare paraśa
Word for word: 
prabhu kahe — the Lord replied; pūrṇa — completely filled; yaiche — just as; dugdhera — of milk; kalasa — container; surā-bindu-pāte — with simply a drop of liquor; keha — anyone; kare — does not; paraśa — touch.
Translation: 
Śrī Caitanya Mahāprabhu then said, “There may be much milk in a big pot, but if it is contaminated by a drop of liquor, it is untouchable.