Sunan an-Nasa'i, Volume 6, Book 51, Hadith 5721 (DarusSalam) ⓘ
It was narrated that Ash-Sha'bi said: "Ali, may Allah be pleased with him, used to give the people thickened grape juice into which flies would fall and not be able to get out again."
أَخْبَرَنَا سُوَيْدٌ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ جَرِيرٍ، عَنْ مُغِيرَةَ، عَنِ الشَّعْبِيِّ، قَالَ كَانَ عَلِيٌّ رضى الله عنه يَرْزُقُ النَّاسَ الطِّلاَءَ يَقَعُ فِيهِ الذُّبَابُ وَلاَ يَسْتَطِيعُ أَنْ يُخْرَجَ مِنْهُ .
also referenced under: Hadith 5718 (Reference) & Book 51, Hadith 180 (In-Book)