Sahih Muslim | Book 1 | Hadith Number 332

Narrated by Zirr b. Hubaish
Zirr b. Hubaish narrated it on the authority of 'Abdullah (that the words of Allah): "Certainly he saw of the greatest signs of Allah" (al-Qur'an, liii. 18) imply that he saw Gabriel in his (original) form and he had six hundred wings.