Husayn ibn al-Harith al-Jadli from the tribe of Jadilah Qays said: The governor of Mecca delivered a speech and said: The Messenger of Allah ﷺ took a pledge from us that we should perform the rites of hajj after sighting the moon. If we do not sight it and two reliable persons bear witness, we should perform the rites of hajj on the basis of their witness. I then asked al-Husayn ibn al-Harith: Who was the governor of Mecca? He replied: I do not know. He then met me later on and told me: He was al-Harith ibn Hatib, brother of Muhammad ibn Hatib. The governor then said: There is among you a man who is more acquainted with Allah and His Apostle than I. He witnessed this from the Messenger of Allah ﷺ. He then pointed with his hand to a man. Al-Husayn said: I asked an old man beside me: Who is that man to whom the governor has alluded? He said: "This is Abdullah ibn Umar, and he spoke the truth. He was more acquainted with Allah than he. He (Abdullah ibn Umar) said: For this is what the Messenger of Allah ﷺ commanded us (to do).  

عَهِدَ إِلَيْنَا رَسُولُ اللَّهِ ﷺ أَنْ نَنْسُكَ لِلرُّؤْيَةِ فَإِنْ لَمْ نَرَهُ وَشَهِدَ شَاهِدَا عَدْلٍ نَسَكْنَا بِشَهَادَتِهِمَا فَسَأَلْتُ الْحُسَيْنَ بْنَ الْحَارِثِ مَنْ أَمِيرُ مَكَّةَ قَالَ لاَ أَدْرِي ثُمَّ لَقِيَنِي بَعْدُ فَقَالَ هُوَ الْحَارِثُ بْنُ حَاطِبٍ أَخُو مُحَمَّدِ بْنِ حَاطِبٍ ثُمَّ قَالَ الأَمِيرُ إِنَّ فِيكُمْ مَنْ هُوَ أَعْلَمُ بِاللَّهِ وَرَسُولِهِ مِنِّي وَشَهِدَ هَذَا مِنْ رَسُولِ اللَّهِ ﷺ وَأَوْمَأَ بِيَدِهِ إِلَى رَجُلٍ قَالَ الْحُسَيْنُ فَقُلْتُ لِشَيْخٍ إِلَى جَنْبِي مَنْ هَذَا الَّذِي أَوْمَأَ إِلَيْهِ الأَمِيرُ قَالَ هَذَا عَبْدُ اللَّهِ بْنُ عُمَرَ وَصَدَقَ كَانَ أَعْلَمَ بِاللَّهِ مِنْهُ فَقَالَ بِذَلِكَ أَمَرَنَا رَسُولُ اللَّهِ ﷺ  

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