The Messenger of Allah [SAW] forbade soaking raisins and dried dates together, and he forbade soaking Al-Busr and dried dates together.  

عَنْ رَسُولِ اللَّهِ ﷺ أَنَّهُ نَهَى أَنْ يُنْبَذَ الزَّبِيبُ وَالتَّمْرُ جَمِيعًا وَنَهَى أَنْ يُنْبَذَ الْبُسْرُ وَالتَّمْرُ جَمِيعًا  

"The Messenger of Allah [SAW] forbade Ad-Dubba', Al-Hantam, Al-Muzaffat, and An-Naqir, and that Al-Busr be mixed with dried dates, and that raisins be mixed with dried dates, and he wrote to the people of Hajar saying: 'Do not mix raisins and dried dates together.'"  

نَهَى رَسُولُ اللَّهِ ﷺ عَنِ الدُّبَّاءِ وَالْحَنْتَمِ وَالْمُزَفَّتِ وَالنَّقِيرِ وَعَنِ الْبُسْرِ وَالتَّمْرِ أَنْ يُخْلَطَا وَعَنِ الزَّبِيبِ وَالتَّمْرِ أَنْ يُخْلَطَا وَكَتَبَ إِلَى أَهْلِ هَجَرَ أَنْ لاَ تَخْلِطُوا الزَّبِيبَ وَالتَّمْرَ جَمِيعًا  

"Al-Busr on their own are unlawful and with dried dates they are unlawful."  

الْبُسْرُ وَحْدَهُ حَرَامٌ وَمَعَ التَّمْرِ حَرَامٌ