Language:
كتاب العلم
3  
Knowledge
(37)
Chapter: It is incumbent on those who are present [in a religious meeting (or conference)] to convey the knowledge to those who are absent
(37)
باب لِيُبَلِّغِ الْعِلْمَ الشَّاهِدُ الْغَائِبَ
Sahih al-Bukhari 105

Narrated Abu Bakra:

The Prophet (ﷺ) said. No doubt your blood, property, the sub-narrator Muhammad thought that Abu Bakra had also mentioned and your honor (chastity), are sacred to one another as is the sanctity of this day of yours in this month of yours. It is incumbent on those who are present to inform those who are absent." (Muhammad the Sub-narrator used to say, "Allah's Messenger (ﷺ) told the truth.") The Prophet (ﷺ) repeated twice: "No doubt! Haven't I conveyed Allah's message to you.

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ عَبْدِ الْوَهَّابِ، قَالَ حَدَّثَنَا حَمَّادٌ، عَنْ أَيُّوبَ، عَنْ مُحَمَّدٍ، عَنِ ابْنِ أَبِي بَكْرَةَ، عَنْ أَبِي بَكْرَةَ، ذُكِرَ النَّبِيُّ صلى الله عليه وسلم قَالَ ‏"‏ فَإِنَّ دِمَاءَكُمْ وَأَمْوَالَكُمْ ـ قَالَ مُحَمَّدٌ وَأَحْسِبُهُ قَالَ وَأَعْرَاضَكُمْ ـ عَلَيْكُمْ حَرَامٌ كَحُرْمَةِ يَوْمِكُمْ هَذَا فِي شَهْرِكُمْ هَذَا، أَلاَ لِيُبَلِّغِ الشَّاهِدُ مِنْكُمُ الْغَائِبَ ‏"‏‏.‏ وَكَانَ مُحَمَّدٌ يَقُولُ صَدَقَ رَسُولُ اللَّهِ صلى الله عليه وسلم كَانَ ذَلِكَ ‏"‏ أَلاَ هَلْ بَلَّغْتُ ‏"‏ مَرَّتَيْنِ‏.‏
Reference : Sahih al-Bukhari 105
In-book reference : Book 3, Hadith 47
USC-MSA web (English) reference : Vol. 1, Book 3, Hadith 105
  (deprecated numbering scheme)