The Scholars Imaam Abu Haneefah, Imaam Ash-Shaafi’ and Imaam Ahmad Bin Hanbal held the opinion that if a fasting person breaks his fast due to forgetfulness he has not broken his fast and nothing is required from him. This is the same whether he ate a lot or a little. Al-Hasan al-Basri, Mujaahid, Ishaq bin Raahuwiyah, Abu Thawr, Daawud bin ‘Ali, ‘Ataa, Al-Awza’i and Al-Laith all held this sam opinion. Rabee’a and Imaam Maalik said: The fast is made faasid by eating and drinking through forgetfulness and Qadaa is required. The correct view is the first and this is supported by the following evidences:
1) Abu Hurairah (ra) said that the Prophet of Allah (saw) said:
“Whoever eats out of forgetfulness and he is fasting then he should complete his fast because verily it is Allah who has given him food and drink”.
Al-Bukhaari (6669), Muslim, Abu Daawud, At-Tirmidhi and Ad-Daarami. The lafzh (wording version) of Muslim (2716) is: “Whoever forgets that he is fasting and then eats or drinks something then he should complete his fast for verily it is Allah who has given him food and drink”
2) Also from Abu Hurairah (ra) that the Prophet (saw) said:
“Whoever breaks his fast in Ramadhaan out of forgetfulness then neither Qadaa nor Kafaarah are not required of him”.
Ibn Hibbaan (3521) and its Sanad is hasan. Ibn Khuzaimah, Ad-Daaraqutni, Al-Bayhaqi and Al-Haakim reported it and verified its soundness (saheeh). Also Ibn Khuzaimah (1990) and At-Tabaraani in Al-Mu’jam al-Awsat mentioned another (similar) hadeeth with the following wording: “Who ever eats or drinks in Ramadhaan out of forgetfulness then there is no Qadaa or Kafaarah required of him”. Its Sanad 9chain) is Hasan.
3) Abu Hurairah (ra) said:
“A man approached the Prophet (saw) and said: O Messenger of Allah, I ate and drank forgetfully and I was fasting. He (saw) responded: Verily Allah provided you with food and drink”.
Abu Daawud (2398), An-Nasaa’i, Ad-Daaraqutni and At-Tirmidhi said it is a Hasan, Saheeh Hadeeth.
4) On the authority of Umm Hakeem bint Deenaar from her mistress Umm Ishaq (ra):
“That she was at the residence of the Messenger (saw) when some porridge was brought so she eat and Dhul Yadayn was with him. The messenger took a bone with a little meat and said: O Umm Ishaq, take some of this. Then I remembered that I had been fasting, so I prevented my hand from moving forward or back. He (saw) asked: What’s wrong? She said: I was fasting but I forgot. Then Dhul Yadayn said: Now you say this after satisfying yourself? Then the Prophet (saw) said: Complete your fasting because this was Rizq (sustenance) that Allah provided for you”. Ahmad (27609), At-Tabaraani in Al-Mu’jam Al-Kabeer.
These evidences provide ample clear proof that the one who breaks his fast out of forgetfulness does not have to make Qadaa or Kafaarah (expiation). This is the same in regard to the obligatory fast of Ramadhaan or any non-obligatory (tatawwu’) fasts. It also does not matter if a little was eaten or drunk or it reached the level of satisfaction. I have not been able to find an evidence for Maalik’s view which is contrary to these evidences. I did not find anything in his most famous recorded works except the verdict that eating and drinking makes the fast faasid. May Allah Ta’aalaa forgive him (in this issue).