Sahih al-Bukhari, Volume 6, Book 60, Hadith 381 (USC-MSA) ⓘ
Narrated `Abdullah: (regarding the revelation) Truly he (Muhammad) did see of the signs of his Lord; the Greatest!' (53.18) The Prophet saw a green screen covering the horizon.
حَدَّثَنَا قَبِيصَةُ، حَدَّثَنَا سُفْيَانُ، عَنِ الأَعْمَشِ، عَنْ إِبْرَاهِيمَ، عَنْ عَلْقَمَةَ، عَنْ عَبْدِ اللَّهِ ـ رضى الله عنه – {لَقَدْ رَأَى مِنْ آيَاتِ رَبِّهِ الْكُبْرَى} قَالَ رَأَى رَفْرَفًا أَخْضَرَ قَدْ سَدَّ الأُفُقَ.
also referenced under: Book 65, Hadith 4858 (In-Book) & Hadith 4858 (DarusSalam)