Sunan Abi Dawud 2456
Narrated Umm Hani:
On the days of the  conquest of Mecca, when Mecca was captured, Fatimah came and sat on the left side of the Messenger of Allah (ﷺ), and Umm Hani was on his right side. A slave-girl brought a vessel which contained some drink; she gave it to him and he drank of it. He then gave it to Umm Hani who drank of it. She said: Messenger of Allah, I have broken my fast; I was fasting. He said to her: Were you making atonement for something? She replied: No. He said: Then it does not harm you if it was voluntary (fast).
حَدَّثَنَا عُثْمَانُ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا جَرِيرُ بْنُ عَبْدِ الْحَمِيدِ، عَنْ يَزِيدَ بْنِ أَبِي زِيَادٍ، عَنْ عَبْدِ اللَّهِ بْنِ الْحَارِثِ، عَنْ أُمِّ هَانِئٍ، قَالَتْ لَمَّا كَانَ يَوْمُ الْفَتْحِ فَتْحِ مَكَّةَ جَاءَتْ فَاطِمَةُ فَجَلَسَتْ عَنْ يَسَارِ رَسُولِ اللَّهِ صلى الله عليه وسلم وَأُمُّ هَانِئٍ عَنْ يَمِينِهِ قَالَتْ فَجَاءَتِ الْوَلِيدَةُ بِإِنَاءٍ فِيهِ شَرَابٌ فَنَاوَلَتْهُ فَشَرِبَ مِنْهُ ثُمَّ نَاوَلَهُ أُمَّ هَانِئٍ فَشَرِبَتْ مِنْهُ فَقَالَتْ يَا رَسُولَ اللَّهِ لَقَدْ أَفْطَرْتُ وَكُنْتُ صَائِمَةً ‏.‏ فَقَالَ لَهَا ‏"‏ أَكُنْتِ تَقْضِينَ شَيْئًا ‏"‏ ‏.‏ قَالَتْ لاَ ‏.‏ قَالَ ‏"‏ فَلاَ يَضُرُّكِ إِنْ كَانَ تَطَوُّعًا ‏"‏ ‏.‏