The Prophet ﷺ forbade mixing dates with raisins, and unripe dates with ripe dates.
أخبرنا يعقوب بن إبراهيم عن يحيى وهو ابن سعيد عن ابن جريج قال أخبرني عطاء
أن النبي ﷺ نهى عن خليط التمر والزبيب والبسر والرطب
Muslim narrated it in Ashribah, chapter on the dislike of mixing dates and raisins when soaking them, hadith 18/1986, from Yahya Qattan, and Bukhari in Ashribah, chapter on those who held that unripe and ripe dates should not be mixed, etc., hadith 5601, from Ibn Jurayj, and it is in Kubra, hadith 5063.