Musnad Ahmad 8:90

'Abd al-Malik ibn 'Amr narrated to us, Fulayh narrated to us, from 'Abd Allah ibn 'Abd al-Rahman ibn Ma'mar, who said: 'Amir ibn Sa'd narrated to 'Umar ibn 'Abd al-'Aziz while he was the governor of Medina: That Sa'd said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever eats seven 'Ajwa dates between the two lava fields of Medina when he wakes up in the morning, nothing will harm him that day until he reaches the evening." Fulayh said: And I think he also said: "And if he eats them when he reaches the evening, nothing will harm him until he wakes up in the morning." 'Umar said: "O 'Amir, look at what you are narrating from the Messenger of Allah (peace and blessings of Allah be upon him)." 'Amir said: "By Allah, I did not lie about Sa'd, and Sa'd did not lie about the Messenger of Allah (peace and blessings of Allah be upon him)."