The Prophet ﷺ decreed that one should not eat two dates together at a time unless he gets the permission from his companions (sharing the meal with him).  

سَمِعْتُ ابْنَ عُمَرَ ؓ يَقُولُ نَهَى النَّبِيُّ ﷺ أَنْ يَقْرُنَ الرَّجُلُ بَيْنَ التَّمْرَتَيْنِ جَمِيعًا حَتَّى يَسْتَأْذِنَ أَصْحَابَهُ  

"While at Medina we were struck with famine. Ibn Az-Zubair used to provide us with dates as our food. Ibn ʿUmar used to pass by us and say, "Don't eat two dates together at a time as the Prophet ﷺ has forbidden eating two dates together at a time (in a gathering) unless one takes the permission of one's companion brother."  

كُنَّا بِالْمَدِينَةِ فَأَصَابَتْنَا سَنَةٌ فَكَانَ ابْنُ الزُّبَيْرِ يَرْزُقُنَا التَّمْرَ وَكَانَ ابْنُ عُمَرَ يَمُرُّ بِنَا فَيَقُولُ لاَ تَقْرُنُوا فَإِنَّ النَّبِيَّ ﷺ نَهَى عَنِ الإِقْرَانِ إِلاَّ أَنْ يَسْتَأْذِنَ الرَّجُلُ مِنْكُمْ أَخَاهُ