Authentic
Sunan Ibn Majah 3332
It was narrated from Sa’d, the freed slave of Abu Bakr – and Sa’d used to serve the Messenger of Allah (ﷺ) and he liked this Hadith – that the Prophet (ﷺ) forbade eating two dates at once.
نَهَى عَنِ الإِقْرَانِ . يَعْنِي فِي التَّمْرِ .