Musnad Ahmad 33:871

Muhammad ibn Ubayd narrated to us, Ubayd Allah ibn al-Walid narrated to us, from Muharib ibn Dithar, who said: Some people from the companions of the Prophet, may Allah bless him and grant him peace, entered upon Jabir ibn Abdullah. He brought bread and vinegar near to them and said: "Eat, for I heard the Messenger of Allah, may Allah bless him and grant him peace, say: 'The best of condiments is vinegar.'"