Sahih Bukhari
Asking Permission
Volume: 008 / Book Number: 074 / Hadith Number: 270
Narrated 'Aisha: that the Prophet said to her, "Gabriel sends Salam (greetings) to you." She replied, "Wa 'alaihi-s-Salam Wa Rahmatu-l-lah." (Peace and Allah's Mercy be on him).