Sahih Bukhari, Hadith: Q104, (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.

صحيح البخاري

Sahih Bukhari

كتاب العلم

The Book of Knowledge

باب ليبلغ العلم الشاهد الغائب:

(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.