It wasnarrated from Sa'd, the freed slave of Abu Bakr – and Sa'dusedto serve the Messenger of Allah (ﷺ) and he liked this Hadith –that the Prophet (ﷺ) forbade eating two dates at once. (ID)
English reference (ID): Vol. 4, Book 29, Hadith 3332 (ID)
Arabic reference (ID): Book 29, Hadith 3457 (ID)