It is narrated from Sayyiduna Junadah al-Azdi (may Allah be pleased with him) that they came to the Messenger of Allah (peace and blessings be upon him) as a group of eight, he (Junadah) himself being the eighth of them, and this was on a Friday. The Messenger of Allah (peace and blessings be upon him) called for food and said to one man: "Eat." He said: "I am fasting." He said to another: "Eat." He too said: "I am fasting," until he had asked all of them. Then he said: "Did you fast yesterday?" They said: "No." He asked: "Will you fast tomorrow?" They said: "No." So he ordered them to break their fast.
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2162