The intention to fast, and the differences reported from Talhah bin Yahya in the narration of 'Aishah about it
أَخْبَرَنِي صَفْوَانُ بْنُ عَمْرٍو، قَالَ حَدَّثَنَا أَحْمَدُ بْنُ خَالِدٍ، قَالَ حَدَّثَنَا إِسْرَائِيلُ، عَنْ سِمَاكِ بْنِ حَرْبٍ، قَالَ حَدَّثَنِي رَجُلٌ، عَنْ عَائِشَةَ بِنْتِ طَلْحَةَ، عَنْ عَائِشَةَ أُمِّ الْمُؤْمِنِينَ، قَالَتْ جَاءَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَوْمًا فَقَالَ " هَلْ عِنْدَكُمْ مِنْ طَعَامٍ " . قُلْتُ لاَ . قَالَ " إِذًا أَصُومَ " . قَالَتْ وَدَخَلَ عَلَىَّ مَرَّةً أُخْرَى فَقُلْتُ يَا رَسُولَ اللَّهِ قَدْ أُهْدِيَ لَنَا حَيْسٌ . فَقَالَ " إِذًا أُفْطِرَ الْيَوْمَ وَقَدْ فَرَضْتُ الصَّوْمَ " .
It was narrated that 'Aishah the mother of the Believers, said: "The Messenger of Allah (ﷺ) came one day and said: 'Do you have any food?' I said: 'No.' He came in to me on another occasion, and I said: 'O Messenger of Allah, we have been given some Hais.' He said: "Then I will break my fast today, although I had started my day fasting."'