Jabir b. Abdullah (Allah be pleased with them) is reported to have said that Messenger of Allah ﷺ forbade the sale of a heap of dates the weight of which is unknown in accordance with the known weight of dates. (Using translation from Muslim 1530a)   

قَالَ سَمِعْتُ جَابِرَ بْنَ عَبْدِ اللهِ يَقُولُ نَهَى رَسُولُ اللهِ ﷺ عَنْ بَيْعِ الصُّبْرَةِ مِنَ التَّمْرِ لَا يُعْلَمُ مَكِيلُهَا بِالْكَيْلِ الْمُسَمَّى مِنَ التَّمْرِ