The Prophet [SAW] forbade mixing Az-Zahuw and dried dates, and mixing Al-Busr and dried dates, and he said: "Soak each one of them on its own in vessels that are tied shut." (Using translation from Nasāʾī 5567)   

أَنَّ النَّبِيَّ ﷺ نَهَى عَنْ خَلِيطِ الزَّهْوِ وَالتَّمْرِ وَخَلِيطِ الزَّبِيبِ وَالتَّمْرِ وَقَالَ انْبِذُوا كُلَّ وَاحِدٍ مِنْهُمَا عَلَى حِدَةٍ فِي الْأَسْقِيَةِ الَّتِي يُلَاثُ عَلَى أَفْوَاهِهَا