مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3839
Musnad of Abdullah bin Mas'ood
Shaqeeq bin Salamah said: I heard Ibn Mas'ood say: The Messenger of Allah (ﷺ) said: "I saw Jibreel at Sidratal-Muntaha; he had six hundred wings.” He said: I asked 'Asim about the wings and he refused to tell me. Then one of his companions told me that the wing (filled the area between) the east and the west.
Musnad Ahmad 3862lts isnad is hasan]