The Book of Purification
2/22. Chapter:
Wiping over the khuff (leather socks)
Sahih Muslim
وَحَدَّثَنَاهُ مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الْوَهَّابِ، قَالَ سَمِعْتُ يَحْيَى بْنَ سَعِيدٍ، بِهَذَا الإِسْنَادِ وَقَالَ فَغَسَلَ وَجْهَهُ وَيَدَيْهِ وَمَسَحَ بِرَأْسِهِ ثُمَّ مَسَحَ عَلَى الْخُفَّيْنِ .
This hadith has been transmitted with the same chain of transmitters by Yahya b. Sa'id with the addition of these words: " He washed his face and hands, and wiped his head and then wiped his socks."
Reference : Sahih Muslim 274bIn-book reference : Book 2, Hadith 94USC-MSA web (English) reference : Book 2, Hadith 525