صحيح مسلم Sahih Muslim كتاب الصيام The Book of Fasting
باب جَوَازِ صَوْمِ النَّافِلَةِ بِنِيَّةٍ مِنَ النَّهَارِ قَبْلَ الزَّوَالِ وَجَوَازِ فِطْرِ الصَّائِمِ نَفْلاً مِنْ غَيْرِ عُذْرٍ:

Chapter: It is permissible to observe a voluntary fast with an intention formed during the day before the sun reaches its Zenith, and it is permissible for one who is observing a voluntary fast to break his fast with no excuse, although it is better for him to complete it

2 hadith
Hadith 1154
وحَدَّثَنَا أَبُو كَامِلٍ فُضَيْلُ بْنُ حُسَيْنٍ ، حَدَّثَنَا عَبْدُ الْوَاحِدِ بْنُ زِيَادٍ ، حَدَّثَنَا طَلْحَةُ بْنُ يَحْيَى بْنِ عُبَيْدِ اللَّهِ ، حَدَّثَتْنِي عَائِشَةُ بِنْتُ طَلْحَةَ ، عَنْ عَائِشَةَ أُمِّ الْمُؤْمِنِينَ رَضِيَ اللَّهُ عَنْهَا ، قَالَتْ : قَالَ لِي رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ذَاتَ يَوْمٍ : " يَا عَائِشَةُ ، هَلْ عِنْدَكُمْ شَيْءٌ ؟ " ، قَالَتْ : فَقُلْتُ : يَا رَسُولَ اللَّهِ ، مَا عِنْدَنَا شَيْءٌ ، قَالَ : " فَإِنِّي صَائِمٌ " ، قَالَتْ : فَخَرَجَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ، فَأُهْدِيَتْ لَنَا هَدِيَّةٌ ، أَوْ جَاءَنَا زَوْرٌ ، قَالَتْ : فَلَمَّا رَجَعَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ، قُلْتُ : يَا رَسُولَ اللَّهِ ، أُهْدِيَتْ لَنَا هَدِيَّةٌ أَوْ جَاءَنَا زَوْرٌ ، وَقَدْ خَبَأْتُ لَكَ شَيْئًا ، قَالَ : " مَا هُوَ ؟ " ، قُلْتُ : حَيْسٌ ، قَالَ : " هَاتِيهِ " ، فَجِئْتُ بِهِ ، " فَأَكَلَ " ، ثُمَّ قَالَ : " قَدْ كُنْتُ أَصْبَحْتُ صَائِمًا " ، قَالَ طَلْحَةُ فَحَدَّثْتُ مُجَاهِدًا بِهَذَا الْحَدِيثِ ، فَقَالَ : ذَاكَ بِمَنْزِلَةِ الرَّجُلِ يُخْرِجُ الصَّدَقَةَ مِنْ مَالِهِ فَإِنْ شَاءَ أَمْضَاهَا ، وَإِنْ شَاءَ أَمْسَكَهَا .
'A'isha, the Mother of the Believers (Allah be pleased with her), reported that one day the Messenger of Allah (ﷺ) said to me: 'A'isha, have you anything (to eat)? I said: 'Messenger of Allah, there is nothing with us. Thereupon he said: I am observing fast. She said: The Messenger of Allah (ﷺ) went out, and there was a present, for us and (at the same time) some visitors dropped in. When the Messenger of Allah (ﷺ) came back, I said to him: Messenger of Allah, a present was given to us, (and in the meanwhile) there came to us visitors (a major Portion of it has been spent on them), but I have saved something for you. He said: What is it? I said: It is hasees (a compound of dates and clarified butter). He said: Bring that. So I brought it to him and he ate it and then said: I woke up in the morning observing fast. Talha said: I narrated this hadith to Mujahid and he said: This (observing of voluntary fast) is like a person who sets apart Sadaqa out of his wealth. He may spend it if he likes, or he may retain it if he so likes.
Hadith Reference Sahih Muslim / The Book of Fasting / Hadith: 1154
Hadith Grading محدثین: أحاديث صحيح مسلم كلها صحيحة
Hadith Takhrij «أحاديث صحيح مسلم كلها صحيحة»
Hadith 1154
وحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ ، حَدَّثَنَا وَكِيعٌ ، عَنْ طَلْحَةَ بْنِ يَحْيَى ، عَنْ عَمَّتِهِ عَائِشَةَ بِنْتِ طَلْحَةَ ، عَنْ عَائِشَةَ أُمِّ الْمُؤْمِنِينَ ، قَالَتْ : دَخَلَ عَلَيَّ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ذَاتَ يَوْمٍ ، فَقَالَ : " هَلْ عِنْدَكُمْ شَيْءٌ " ، فَقُلْنَا : لَا ، قَالَ : " فَإِنِّي إِذَنْ صَائِمٌ " ، ثُمَّ أَتَانَا يَوْمًا آخَرَ ، فَقُلْنَا : يَا رَسُولَ اللَّهِ ، أُهْدِيَ لَنَا حَيْسٌ ، فَقَالَ : " أَرِينِيهِ فَلَقَدْ أَصْبَحْتُ صَائِمًا ، فَأَكَلَ " .
'A'isha, the Mother of the Believers (Allah be pleased with her), reported: The Apostle of Allah (ﷺ) came to me one day and said: Is there anything with you (to eat)? I said: No. Thereupon he said: I shall then be fasting. Then he came to us another day and we said: Messenger of Allah, has been offered to us as a gift. Thereupon he said: Show that to me; I had been fasting since morning. He then ate it.
Hadith Reference Sahih Muslim / The Book of Fasting / Hadith: 1154
Hadith Grading محدثین: أحاديث صحيح مسلم كلها صحيحة
Hadith Takhrij «أحاديث صحيح مسلم كلها صحيحة»