Sahih Muslim Book - 22, Hadith - 4080

حَدَّثَنَا هَارُونُ بْنُ مَعْرُوفٍ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ وَهْبٍ أَخْبَرَنِى عَمْرٌو ح وَحَدَّثَنِى أَبُو الطَّاهِرِ أَخْبَرَنَا ابْنُ وَهْبٍ عَنْ عَمْرِو بْنِ الْحَارِثِ أَنَّ أَبَا النَّضْرِ حَدَّثَهُ أَنَّ بُسْرَ بْنَ سَعِيدٍ حَدَّثَهُ عَنْ مَعْمَرِ بْنِ عَبْدِ اللَّهِ أَنَّهُ أَرْسَلَ غُلاَمَهُ بِصَاعِ قَمْحٍ فَقَالَ بِعْهُ ثُمَّ اشْتَرِ بِهِ شَعِيرًا. فَذَهَبَ الْغُلاَمُ فَأَخَذَ صَاعًا وَزِيَادَةَ بَعْضِ صَاعٍ فَلَمَّا جَاءَ مَعْمَرًا أَخْبَرَهُ بِذَلِكَ فَقَالَ لَهُ مَعْمَرٌ لِمَ فَعَلْتَ ذَلِكَ انْطَلِقْ فَرُدَّهُ وَلاَ تَأْخُذَنَّ إِلاَّ مِثْلاً بِمِثْلٍ فَإِنِّى كُنْتُ أَسْمَعُ رَسُولَ اللَّهِ -صلى الله عليه وسلم- يَقُولُ « الطَّعَامُ بِالطَّعَامِ مِثْلاً بِمِثْلٍ ». قَالَ وَكَانَ طَعَامُنَا يَوْمَئِذٍ الشَّعِيرَ. قِيلَ لَهُ فَإِنَّهُ لَيْسَ بِمِثْلِهِ قَالَ إِنِّى أَخَافُ أَنْ يُضَارِعَ.

It was narrated from Ma'mar bin 'Abdullah that he sent his slave with a Sa' of wheat and he said: "Sell it then buy barley." The slave went and took a Sa' and part of a Sa' more. When he came to Ma'mar he told him about that, and Ma'mar said to him: "Why did you do that? Go and give it back, and do not take anything but like for like, for I used to hear the Messenger of Allah (s.a.w) say: 'Food for food, like for like.' And our food at that time was barley. It was said to him: 'It is not like it.' He said: 'I am afraid that it may be similar."'