ENOfficial
Narrated Ibn `Abbas: I heard the Prophet (ﷺ) delivering a sermon at `Arafat saying, "If a Muhrim does not find slippers, he could wear Khuffs (socks made from thick fabric or leather, but he has to cut short the Khuffs below the ankles), and if he does not find an Izar (a waist sheet for wrapping the lower half of the body) he could wear trousers."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَبُو الْوَلِيدِ، حَدَّثَنَا شُعْبَةُ، قَالَ أَخْبَرَنِي عَمْرُو بْنُ دِينَارٍ، سَمِعْتُ جَابِرَ بْنَ زَيْدٍ، سَمِعْتُ ابْنَ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَخْطُبُ بِعَرَفَاتٍ " مَنْ لَمْ يَجِدِ النَّعْلَيْنِ فَلْيَلْبَسِ الْخُفَّيْنِ، وَمَنْ لَمْ يَجِدْ إِزَارًا فَلْيَلْبَسْ سَرَاوِيلَ ". لِلْمُحْرِمِ.
sunnah.com