Musnad Ahmad 33:800

'Affan narrated to us, Hammam narrated to us, he said: Sulayman ibn Musa asked 'Ata', and I was a witness, he said: Did Jabir narrate to you, "That the Messenger of Allah (peace and blessings of Allah be upon him) forbade that unripe dates and dried dates be steeped together, and that raisins and dried dates be steeped together?" 'Ata' said: Yes.