Salim (may Allah have mercy on him) narrates from his father (Sayyiduna Abdullah bin Umar, may Allah be pleased with them both) that Sayyiduna Sa'd bin Abi Waqqas (may Allah be pleased with him) asked Sayyiduna Umar (may Allah be pleased with him) about wiping over leather socks (khuffs), and Sayyiduna Umar (may Allah be pleased with him) said: "I heard the Messenger of Allah (peace and blessings be upon him) command wiping over the back (upper surface) of the leather socks when they have been put on in a state of purity."
Hadith Referenceمسند أبي يعلى الموصلي / مسند عمر بن الخطاب رضي الله عنه / 170
Hadith Takhrij«قال سعيد بن محمد السناري: صحيح لغيره» «أخرجه مجمع الزوائد ومنبع الفوائد برقم: 1352، مسند ابویعلیٰ ترقیم الاثری: 165»