On the authority of a man from the Companions of the Prophet ﷺ: People differed among themselves on the last day of Ramadan (about the appearance of the moon of Shawwal). Then two bedouins came and witnessed before the Prophet ﷺ swearing by Allah that they had sighted moon the previous evening. So the Messenger of Allah ﷺ commanded the people to break the fast. The narrator Khalaf has added in his version: "and that they should proceed to the place of prayer (for 'Id)".
عَنْ رَجُلٍ مِنْ أَصْحَابِ النَّبِيِّ ﷺ قَالَ اخْتَلَفَ النَّاسُ فِي آخِرِ يَوْمٍ مِنْ رَمَضَانَ فَقَدِمَ أَعْرَابِيَّانِ فَشَهِدَا عِنْدَ رَسُولِ اللَّهِ ﷺ بِاللَّهِ لأَهَلاَّ الْهِلاَلَ أَمْسِ عَشِيَّةً فَأَمَرَ رَسُولُ اللَّهِ ﷺ النَّاسَ أَنْ يُفْطِرُوا زَادَ خَلَفٌ فِي حَدِيثِهِ وَأَنْ يَغْدُوا إِلَى مُصَلاَّهُمْ