Malik related to me that Yahya ibn Said heard Said ibn al-Musayyab say, "When you come to a land where they give full measureand full weight, stay there. When you come to a land where theyshorten the measure and weight, then do not stay there very long." (IT)
USC-MSA web (English) reference: Book 31, Hadith 100 (IT)
Arabic reference (IT): Book 31, Hadith 1386 (IT)