Sahih Bukhari Volume 8, Book 73, Hadith Number 220.

Narated By ‘Aisha : (The wife the Prophet) Allah’s Apostle said, “O ‘Aisha! This is Gabriel sending his greetings to you.” I said, “Peace, and Allah’s Mercy be on him.” ‘Aisha added: The Prophet used to see things which we used not to see.