Musnad Ahmad 1309:2

Abu Nu'aym narrated to us, Isra'il narrated to us, from Zayd ibn Jubayr, from Abu Yazid al-Danni, from Maymunah, the freed slave woman of the Prophet, may Allah bless him and grant him peace, who said: The Messenger of Allah, may Allah bless him and grant him peace, was asked about a man who kissed his wife while he was fasting. He said: "They have both broken their fast."