Musnad Abu Ya'la al-Mawsili 6:98

Uthman ibn Abi Shaybah narrated to us, Ibn Idris narrated to us, from Muhammad ibn Ammarah, from Abdullah ibn Abd al-Rahman ibn Ma'mar: Amir ibn Sa'd informed me, from his father, who said: I heard the Prophet, may Allah bless him and grant him peace, saying: "No man consumes seven dates in the morning from what is between its two lava fields, such that poison harms him that day."