Sunan Ibn Majah Book 7, Hadith 1701

حَدَّثَنَا إِسْمَاعِيلُ بْنُ مُوسَى، حَدَّثَنَا شَرِيكٌ، عَنْ طَلْحَةَ بْنِ يَحْيَى، عَنْ مُجَاهِدٍ، عَنْ عَائِشَةَ، قَالَتْ دَخَلَ عَلَىَّ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ فَقَالَ: ‏"‏ هَلْ عِنْدَكُمْ شَىْءٌ؟ ‏"‏ ‏.‏ فَنَقُولُ: لاَ ‏.‏ فَيَقُولُ: ‏"‏ إِنِّي صَائِمٌ ‏"‏ ‏.‏ فَيُقِيمُ عَلَى صَوْمِهِ ثُمَّ يُهْدَى لَنَا شَىْءٌ فَيُفْطِرُ ‏.‏ قَالَتْ: وَرُبَّمَا صَامَ وَأَفْطَرَ ‏.‏ قُلْتُ: كَيْفَ ذَا؟ قَالَتْ: إِنَّمَا مَثَلُ هَذَا مَثَلُ الَّذِي يَخْرُجُ بِصَدَقَةٍ فَيُعْطِي بَعْضَهَا وَيُمْسِكُ بَعْضًا ‏.‏

It was narrated that ‘Aishah said:“The Messenger of Allah (ﷺ) would enter upon me and say: ‘Do you have anything (any food)?’ If we said: ‘No,’ he would say: ‘Then I am fasting.’ So he would continue fasting, then it we were given some food, he would break his fast.” She said: “Sometimes he would fast and (then) break fast (i.e., combine fasting and breaking fast in one day).” I said: “How is that?” She said: “Like the one who goes out with charity (i.e., something to give in charity),and he gives some away and keeps some.”