From Sahih Bukhari (Hadith 4980):
Narrated Abu `Uthman:I was informed that Gabriel came to the Prophet (ﷺ) while Um Salama was with him. Gabriel started talking (to the Prophet). Then the Prophet (ﷺ) asked Um Salama, "Who is this?" She replied, "He is Dihya (al-Kalbi)." When Gabriel had left, Um Salama said, "By Allah, I did not take him for anybody other than him (i.e. Dihya) till I heard the sermon of the Prophet (ﷺ) wherein he informed about the news of Gabriel." The subnarrator asked Abu `Uthman: From whom have you heard that? Abu `Uthman said: From Usama bin Zaid
Reference: Bukhari 4980