(11) باب مَنْ رَأَى أَنْ لاَ يَخْلِطَ الْبُسْرَ وَالتَّمْرَ إِذَا كَانَ مُسْكِرًا وَأَنْ لاَ يَجْعَلَ إِدَامَيْنِ فِي إِدَامٍ
Narrated Abu Qatada:
The Prophet (ﷺ) forbade the mixing of ripe and unripe dates and also the mixing of dates and raisins (for preparing a syrup) but the syrup of each kind of fruit should be prepared separately. ( One may have such drinks as long as it is fresh )
Reference: Sahih al-Bukhari 5602
In-book reference: Book 74, Hadith 28
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 7, Book 69, Hadith 507