Abu Sa'id reported that Allah's Apostle ﷺ prohibited that fresh dates and grapes be mixed together and that fresh dates and unripe dates be mixed together. (Using translation from Muslim 1987a)
«نَهَى رَسُولُ اللهِ ﷺ عَنِ الْجَرِّ أَنْ يُنْبَذَ فِيهِ وَعَنِ التَّمْرِ وَالْبُسْرِ أَنْ يُخْلَطَ بَيْنَهُمَا وَعَنِ التَّمْرِ وَالزَّبِيبِ أَنْ يُخْلَطَ بَيْنَهُمَا»