From Sahih Bukhari (Hadith 3235):
Narrated 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 (ﷺ) 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
Reference: Bukhari 3235