حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ زَيْدِ بْنِ أَسْلَمَ، عَنْ عَطَاءِ بْنِ يَسَارٍ، أَنَّهُ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ التَّمْرُ بِالتَّمْرِ مِثْلاً بِمِثْلٍ ‏"‏ ‏.‏ فَقِيلَ لَهُ إِنَّ عَامِلَكَ عَلَى خَيْبَرَ يَأْخُذُ الصَّاعَ بِالصَّاعَيْنِ ‏.‏ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ ادْعُوهُ لِي ‏"‏ ‏.‏ فَدُعِيَ لَهُ فَقَالَ لَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ أَتَأْخُذُ الصَّاعَ بِالصَّاعَيْنِ ‏"‏ ‏.‏ فَقَالَ يَا رَسُولَ اللَّهِ لاَ يَبِيعُونَنِي الْجَنِيبَ بِالْجَمْعِ صَاعًا بِصَاعٍ ‏.‏ فَقَالَ لَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ بِعِ الْجَمْعَ بِالدَّرَاهِمِ ثُمَّ ابْتَعْ بِالدَّرَاهِمِ جَنِيبًا ‏"‏ ‏.‏

Yahya related to me from Malik from Zayd ibn Aslam that Ata ibnYasar said, "The Messenger of Allah, may Allah bless him and grant himpeace, said, 'Dried dates for dried dates is like for like.' It wassaid to him, 'Your agent in Khaybar takes one sa for two.' TheMessenger of Allah, may Allah bless him and grant him peace, said,'all him to me.' So he was called for. The Messenger of Allah, mayAllah bless him and grant him peace, asked, 'Do you take one sa fortwo?' He replied, 'Messengerof Allah! Why should they sell me gooddates for assorted low quality dates, sa for sa!' The Messenger ofAllah, may Allah bless him and grant him peace, said, 'Sell theassorted ones for dirhams, and then buy the good ones with thosedirhams.' " Translation Not Available

Book Ref: Muwatta Imam Malik Book 31 Hadith 1313
Web Ref:  Muwatta Imam Malik Book 31 Hadith 20