مُوَطَّأُ مَالِكٍ
Muwatta Malik 1386
Business Transactions
وَحَدَّثَنِي مَالِكٌ، عَنْ يَحْيَى بْنِ سَعِيدٍ، أَنَّهُ سَمِعَ سَعِيدَ بْنَ الْمُسَيَّبِ، يَقُولُ إِذَا جِئْتَ أَرْضًا يُوفُونَ الْمِكْيَالَ وَالْمِيزَانَ فَأَطِلِ الْمُقَامَ بِهَا وَإِذَا جِئْتَ أَرْضًا يُنَقِّصُونَ الْمِكْيَالَ وَالْمِيزَانَ فَأَقْلِلِ الْمُقَامَ بِهَا .
Malik related to me that Yahya ibn Said heard Said ibn al- Musayyab say, "When you come to a land where they give full measure and full weight, stay there. When you come to a land where they shorten the measure and weight, then do not stay there very long."
Arabic/English book reference: Book 31, Hadith 100