The Book of Drinks (Kitab Al-Ashriba)
Muslim :: Book 23 : Hadith 5093
Jabir b. 'Abdullah reported that Allah's Apostle (may peace be upon him) asked his family for condiment. They (the members of his household) said: We have nothing with us but vinegar. He asked for it, he began to eat it, and then said: Vinegar is a good condiment, vinegar is a good condiment.