Sahih Muslim 1179
Sahih Muslim · Book 15: The Book of Pilgrimage · What one who has entered Ihram for Hajj or Umrah is permitted to wear, and what is not permissible, and perfume is forbidden for him
Jabir (Allah be pleased with him) reported Allah's Messenger (ﷺ) as saying:
وَحَدَّثَنَا أَحْمَدُ بْنُ عَبْدِ اللَّهِ بْنِ يُونُسَ ، حَدَّثَنَا زُهَيْرٌ ، حَدَّثَنَا أَبُو الزُّبَيْرِ ، عَنْ جَابِرٍ ، - رضى الله عنه - قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ لَمْ يَجِدْ نَعْلَيْنِ فَلْيَلْبَسْ خُفَّيْنِ وَمَنْ لَمْ يَجِدْ إِزَارًا فَلْيَلْبَسْ سَرَاوِيلَ " .
He who does not find shoes to wear may wear socks, and he who does not find lower garment to wear may put on trousers.