Sahih Muslim Book 023, Hadith Number 5096.
Chapter : The merit of vinegar as a condiment.
Jabir b. 'Abdullah reported: While I was sitting in my house there happened to pass by me Allah's Messenger (may peace be upon him). He made a gesture to me and I stood up for him. He took hold of my hand until we came to one of the apartments of his wives. He entered and then asked me to get in. So I entered and there was hanging a curtain beside her. He (the Holy Prophet) said: Is there any food (with you)? They (the members of the household) said: Yes And then there were brought three loaves of bread for him (the Holy Prophet) and placed in the basket of palm leaves. Allah's Messenger (may peace be upon him) picked up one loaf and placed that before him, and then picked up another one and placed it before me. He then picked up the third one and broke it into two parts, and kept the one-half before him and the other half before me, and then said: Is there any condiment? They (the members of the household) said: There is nothing (in the form of condiment) but some vinegar only. He said: Bring that, for vinegar is a good condiment.