Musnad Ahmad 26:193

Yahya ibn Adam narrated to us, Israel narrated to us, from Abu Ishaq, from Abd al-Rahman ibn Yazid, from Abdullah, regarding His saying: {The heart did not lie [about] what it saw} [An-Najm: 11]. He said: "The Messenger of Allah, may Allah bless him and grant him peace, saw Gabriel in a garment of green silk (rafraf), having filled what is between the heaven and the earth."