Sunan an-Nasa'i
It was narrated that Ibn 'Abbas said: "Al-Busr on their own are unlawful and with dried dates they are unlawful."
أَخْبَرَنَا أَحْمَدُ بْنُ سُلَيْمَانَ، قَالَ حَدَّثَنَا يَزِيدُ، قَالَ أَنْبَأَنَا حُمَيْدٌ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، قَالَ الْبُسْرُ وَحْدَهُ حَرَامٌ وَمَعَ التَّمْرِ حَرَامٌ.
Grade: Sahih (Darussalam)
Reference