Sayyidah Umm Ma'bad bin Ka'b (may Allah be pleased with her), who had prayed towards both qiblahs, narrates that the Messenger of Allah (peace and blessings be upon him) said: "Do not make nabidh by mixing dates and raisins; rather, make nabidh from each of them separately."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21816