✅ Answer:

1 عَنِ الْحَلَبِيِّ عَنْ أَبِي عَبْدِ اللَّهِ أَنَّهُ سُئِلَ عَنْ رَجُلٍ نَسِيَ فَأَكَلَ وَ شَرِبَ ثُمَّ ذَكَرَ قَالَ لَا يُفْطِرْ إِنَّمَا هُوَ شَيْ ءٌ رَزَقَهُ اللَّهُ فَلْيُتِمَّ صَوْمَهُ.

📚 Al-Faqih, Vol.2, p.118

A question was asked to Imam al-Sadiq (peace be upon him) about a man who, while fasting, forgot and ate and drank! Then he remembered. He said: It does not break his fast, for it was something that Allah provided him, so he should complete his fast!

📚 Al-Faqih, Vol.2, p.118

2 عَنْ عَمَّارِ بْنِ مُوسَى أَنَّهُ سَأَلَ أَبَا عَبْدِ اللَّهِ عَنِ الرَّجُلِ يَنْسَى وَ هُوَ صَائِمٌ فَیُجَامَعَ أَهْلَهُ فَقَالَ يَغْتَسِلُ وَ لَا شَيْ ءَ عَلَيْهِ.

Ammar ibn Musa asked Imam al-Sadiq (peace be upon him) about a man who, while fasting, forgets and has intercourse with his spouse. He replied: He should perform ghusl (ritual bath), and nothing is required of him!

📚 Al-Faqih, Vol.2, p.118

3 قَالَ وَ رُوِيَ عَنِ الْأَئِمَّةِ أَنَّ هَذَا فِي شَهْرِ رَمَضَانَ وَ غَيْرِهِ وَ لَا يَجِبُ مِنْهُ الْقَضَاءُ.

Sheikh Saduq said: The Imams (peace be upon them) narrated that this ruling applies to Ramadan and other times, and making up the fast (qada) is not necessary for these cases!

📚 Al-Kafi, Vol.4, p.101

4 عَنْ دَاوُدَ بْنِ سِرْحَانَ عَنْ أَبِي عَبْدِ اللَّهِ فِي الرَّجُلِ يَنْسَى وَ يَأْكُلُ فِي شَهْرِ رَمَضَانَ- قَالَ يُتِمُّ صَوْمَهُ فَإِنَّمَا هُوَ شَيْ ءٌ أَطْعَمَهُ اللَّهُ

Imam al-Sadiq (peace be upon him) said regarding a person who forgets and eats during Ramadan: He should complete his fast, for it certainly was something Allah provided for him!

📚 Al-Tahdhib, Vol.4, p.268

5 عَنْ مُحَمَّدِ بْنِ قَيْسٍ عَنْ أَبِي جَعْفَرٍ قَالَ كَانَ أَمِيرُ الْمُؤْمِنِينَ يَقُولُ مَنْ صَامَ فَنَسِيَ فَأَكَلَ أَوْ شَرِبَ فَلَا يُفْطِرُ مِنْ أَجْلِ أَنَّهُ نَسِيَ فَإِنَّمَا هُوَ رِزْقٌ رَزَقَهُ اللَّهُ تَعَالَى فَلْيُتِمَّ صِيَامَهُ

Imam al-Baqir (peace be upon him) said: Imam Ali (peace be upon him) said: Whoever fasts and forgets, then eats or drinks, should not break his fast because he forgot, and it certainly was sustenance that Allah provided, so he should complete his fast.

📚 Al-Kafi, Vol.4, p.86

Zuhri narrates from Imam al-Sajjad (peace be upon him) who said: As for a permissible fast, for someone who eats, drinks, or vomits unintentionally out of forgetfulness, Allah has made it lawful for him, and his fast is sufficient.

6 عَنِ الزُّهْرِيِّ عَنْ عَلِيِّ بْنِ الْحُسَيْنِ فِي حَدِيثٍ قَالَ: وَ أَمَّا صَوْمُ الْإِبَاحَةِ لِمَنْ أَكَلَ أوَ شَرِبَ نَاسِياً أَوْ قَاءَ مِنْ غَيْرِ تَعَمُّدٍ فَقَدْ أَبَاحَ اللَّهُ لَهُ ذَلِكَ وَ أَجْزَأَ عَنْهُ صَوْمُهُ.

✅ From the above narrations, it is clear that eating, drinking, or sexual intercourse out of forgetfulness does not invalidate any type of fast, whether it is during Ramadan or at other times, and the person should complete their fast with nothing required of them.