It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) and Sayyiduna Hasan (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him and his family) said: When any one of you is fasting and he eats or drinks forgetfully, then he should complete his fast, for it is Allah Almighty who has fed him and given him drink.

Umm Hakim narrates that Sayyida Umm Ishaq (may Allah be pleased with her) said: I was present in the service of the Messenger of Allah (peace and blessings be upon him), a bowl of tharid was brought to him, I and Sayyiduna Dhul-Yadayn (may Allah be pleased with him) also ate that food with the Prophet (peace and blessings be upon him). The Messenger of Allah (peace and blessings be upon him) gave me a bone with meat on it and said: Umm Ishaq! Eat this as well. At that moment, I remembered that I was fasting. My hand stopped right there; I could neither move it forward nor backward. The Prophet (peace and blessings be upon him) said: What has happened to you? I said: I was fasting and I forgot. Sayyiduna Dhul-Yadayn (may Allah be pleased with him) said: Now you remembered, after being full. But the Noble Prophet (peace and blessings be upon him) said: Complete your fast, because Allah Almighty has provided this sustenance for you.

It is narrated from Sayyida Asma bint Abi Bakr (may Allah be pleased with her), she says: During the time of the Messenger of Allah (peace and blessings be upon him), on one day in the month of Ramadan, clouds appeared (and we thought that the sun had set), so we broke our fast, but later the sun became visible. I (Abu Usama) asked Hisham: So were the people ordered to make up that fast? He said: Is there any other option besides this?