Sahih Bukhari Volume 4, Book 54, Hadith Number 458.

Narated By Masruq : I asked ‘Aisha “What about His Statement: “Then he (Gabriel) approached And came closer, And was at a distance Of but two bow-lengths Or (even) nearer?” (53.8-9) She replied, “It was Gabriel who used to come to the Prophet in the figure of a man, but on that occasion, he came in his actual and real figure and (he was so huge) that he covered the whole horizon.”