Musnad Ahmad 15:1

Sulayman ibn Dawud—meaning Abu Dawud al-Tayalisi—narrated to us, Abu ‘Amir al-Khazzaz narrated to us, from al-Hasan, from Sa‘d, the freed slave of Abu Bakr, who said: Dates were placed before the Messenger of Allah, may Allah bless him and grant him peace, and they began to pair them [eating two at a time]. The Messenger of Allah, may Allah bless him and grant him peace, said: "Do not pair them."