"The Prophet said: ' A heap of grain should not be sold for a heap of grain, or for a heap of grain of known measure. " (Using translation from Nasāʾī 4548)  

قَالَ النَّبِيُّ ﷺ «لَا تُبَاعُ الصُّبْرَةُ مِنَ الطَّعَامِ بِالصُّبْرَةِ مِنَ الطَّعَامِ وَلَا الصُّبْرَةُ مِنَ الطَّعَامِ بِالْكَيْلِ مِنَ الطَّعَامِ الْمُسَمَّى»