Sunan an-Nasa'i, Volume 6, Book 51, Hadith 5545 (DarusSalam) ⓘ
It was narrated that Anas bin Malik said: "When Khamr was forbidden, their drink was (made from) unripe dates and dried dates."
أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ حُمَيْدٍ الطَّوِيلِ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ حُرِّمَتِ الْخَمْرُ حِينَ حُرِّمَتْ وَإِنَّهُ لَشَرَابُهُمُ الْبُسْرُ وَالتَّمْرُ.
also referenced under: Hadith 5543 (Reference) & Book 51, Hadith 4 (In-Book)