Musnad Ahmad 1167:16

Abu Usamah narrated to us, from Hisham, from Fatimah, from Asma, who said: "We broke our fast during the time of the Messenger of Allah, peace and blessings of Allah be upon him, on a cloudy day in Ramadan, then the sun appeared." I said to Hisham: "Were they ordered to make up for it?" He said: "And is there any escape from that?"