I entered the Prophet's ﷺ house with him, and there were pieces of bread and vinegar. The Messenger of Allah ﷺ said, "Eat, for vinegar is an excellent condiment."
أخبرنا عمرو بن علي قال حدثنا يحيى قال حدثنا المثنى بن سعيد قال حدثنا طلحة بن نافع
دخلت مع النبي ﷺ بيته فإذا فلق وخل فقال رسول الله ﷺ كل فنعم الإدام الخل
No references are available.
Muslim narrated it in the Book of Drinks, Chapter on the merit of vinegar and eating it as a condiment, no. 1052/2052, from the hadith of Muthanna bin Saeed with this wording. It is also found in Kubra, no. 4738.