Musnad Ahmad 33:301

Yahya ibn Sa'id narrated to us, from 'Abd al-Malik, 'Ata' informed me, from Jabir ibn 'Abdullah, he said: "The Messenger of Allah, may Allah bless him and grant him peace, forbade mixing fresh dates (rutab) and unripe dates (busr), and dates (tamr) and raisins (zabib)."