From Sahih Muslim (Hadith 404):
This hadith has been narrated on the authority of 'A'isha with another chain of narrators like one transmitted by Yunus, i. e. the first thing with which the revelation was initiated with the Messenger of Allah (ﷺ) except the words:By Allah, Allah would never humiliate you, and Khadija said: O son of my uncle! Listen to the son of your brother
Reference: Muslim 404