The Prophet ﷺ said, "What an excellent condiment vinegar is."
حدثنا أبو الوليد الطيالسي ومسلم بن إبراهيم قالا حدثنا المثنى بن سعيد عن طلحة بن نافع
عن النبي ﷺ قال نعم الإدام الخل
No references are available.
Related by Muslim in the Book of Drinks, chapter on the virtue of vinegar and eating it as a condiment, hadith no. 2052, from the hadith of Muthanna Ibn Saeed, with this wording.