وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ عَنِ الْقَاسِمِ بْنِ مُحَمَّدٍ، أَنَّهُ قَالَ قَالَ عُمَرُ بْنُ الْخَطَّابِ الدِّينَارُ بِالدِّينَارِ وَالدِّرْهَمُ بِالدِّرْهَمِ وَالصَّاعُ بِالصَّاعِ وَلاَ يُبَاعُ كَالِئٌ بِنَاجِزٍ ‏.‏

Yahya related to me from Malik that he had heard that al-Oasimibn Muhammad said, ''Umar ibn al-Khattab said, 'A dinar for a dinar,and a dirham for adirham, and a sa for a sa. Something to be collectedlater is not to be sold for something at hand. ' " Translation Not Available

Book reference: Muwatta Imam Malik Book 31 Hadith 1327
Web reference: Muwatta Imam Malik Book 31 Hadith 36