The Messenger of Allah ﷺ said, "Do not mix raisins and dates together, nor unripe dates and ripe dates."
أخبرنا عمرو بن علي عن أبي داود قال حدثنا بسطام قال حدثنا مالك بن دينار عن عطاء
أن رسول الله ﷺ قال لا تخلطوا الزبيب والتمر ولا البسر والتمر
Its isnad is sahih, and it is agreed upon (Bukhari and Muslim) from the hadith of Ataa on this same account. See the previous and following hadith. The hadith is in Kubra, no. 5064.* Bustam is Ibn Muslim.