Sahih al-Bukhari, Volume 7, Book 63, Hadith 215 (USC-MSA) ⓘ

Narrated Ibn `Abbas: Allah's Messenger performed the Tawaf (around the Ka`ba while riding his camel, and every time he reached the corner (of the Black Stone) he pointed at it with his hand and said, "Allahu Akbar." (Zainab said: The Prophet said, "An opening has been made in the wall of Gog and Magog like this and this," forming the number 90 (with his thumb and index finger).

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ، حَدَّثَنَا أَبُو عَامِرٍ عَبْدُ الْمَلِكِ بْنُ عَمْرٍو، حَدَّثَنَا إِبْرَاهِيمُ، عَنْ خَالِدٍ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، قَالَ طَافَ رَسُولُ اللَّهِ صلى الله عليه وسلم عَلَى بَعِيرِهِ، وَكَانَ كُلَّمَا أَتَى عَلَى الرُّكْنِ أَشَارَ إِلَيْهِ، وَكَبَّرَ‏.‏ وَقَالَتْ زَيْنَبُ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏ "‏ فُتِحَ مِنْ رَدْمِ يَأْجُوجَ وَمَأْجُوجَ مِثْلُ هَذِهِ ‏" ‏‏.‏ وَعَقَدَ تِسْعِينَ‏.‏