Do not prepare Nabidh by mixing nearly ripe dates and fresh dates together, and do not prepare Nabidh by mixing grapes and dates together, but prepare Nabidh from each (one of them) separately. (Using translation from Muslim 1988a)   

عَنِ النَّبِيِّ ﷺ قَالَ «لَا تَنْتَبِذُوا الزَّهْوَ وَالرُّطَبَ جَمِيعًا وَلَا تَنْتَبِذُوا الزَّبِيبَ وَالتَّمْرَ جَمِيعًا وَانْتَبِذُوا كُلَّ وَاحِدٍ مِنْهُمَا عَلَى حِدَتِهِ»