The Messenger of Allah ﷺ forbade soaking unripe and ripe dates together to make nabidh.
حدثنا قتيبة حدثنا الليث بن سعد عن عطاء بن أبي رباح
أن رسول الله ﷺ نهى أن ينبذ البسر والرطب جميعا
Agreed upon. Muslim also reported it, in the Book of Drinks, chapter on the disapproval of soaking dates and raisins mixed together, hadith no. 1986, from Qutayba, and Bukhari, hadith no. 5601, from the hadith of Ata bin Abu Rabah, with the same chain.