Sunan an-Nasa'i, Volume 6, Book 51, Hadith 5565 (DarusSalam) ⓘ

It was narrated that Anas bin Malik said: "The Messenger of Allah [SAW] forbade us to soak two things together when one is more potent than the other. I asked him about Fadikh (a drink made from fresh dates cut open) and he forbade it. He disliked the extra bit on Al-Busr, fearing that that might make it two things, so we used to cut it off."

أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ وِقَاءِ بْنِ إِيَاسٍ، عَنِ الْمُخْتَارِ بْنِ فُلْفُلٍ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ نَهَى رَسُولُ اللَّهِ صلى الله عليه وسلم أَنْ نَجْمَعَ شَيْئَيْنِ نَبِيذًا يَبْغِي أَحَدُهُمَا عَلَى صَاحِبِهِ ‏.‏ قَالَ وَسَأَلْتُهُ عَنِ الْفَضِيخِ فَنَهَانِي عَنْهُ قَالَ كَانَ يَكْرَهُ الْمُذَنَّبَ مِنَ الْبُسْرِ مَخَافَةَ أَنْ يَكُونَا شَيْئَيْنِ فَكُنَّا نَقْطَعُهُ ‏.‏