Sunan an-Nasa'i, Book 51, Hadith 30 (In-Book) ⓘ

It was narrated that Abu Sa'eed Al-Khudri said: "The Messenger of Allah [SAW] forbade mixing Al-Busr with dried dates, or raisins with dried dates, or raisins with Al-Busr, and he said: 'Whoever among you (wants to) drink them, let him drink each one of them on its own: dried dates on their own, or Al-Busr on their own, or raisins on their own."

أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ إِسْمَاعِيلَ بْنِ مُسْلِمٍ الْعَبْدِيِّ، قَالَ حَدَّثَنَا أَبُو الْمُتَوَكِّلِ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ، قَالَ نَهَى رَسُولُ اللَّهِ صلى الله عليه وسلم أَنْ يُخْلَطَ بُسْرٌ بِتَمْرٍ أَوْ زَبِيبٌ بِتَمْرٍ أَوْ زَبِيبٌ بِبُسْرٍ وَقَالَ ‏ "‏ مَنْ شَرِبَهُ مِنْكُمْ فَلْيَشْرَبْ كُلَّ وَاحِدٍ مِنْهُ فَرْدًا تَمْرًا فَرْدًا أَوْ بُسْرًا فَرْدًا أَوْ زَبِيبًا فَرْدًا ‏" ‏ ‏.‏