Hadith 3:220
He also said, “I saw the Prophet wiping over the upper part of his shoes.” Tirmidhi and Abu Dawud transmitted it.
وَعنهُ قَالَ: رَأَيْتُ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يمسح على الْخُفَّيْنِ على ظاهرهما. رَوَاهُ التِّرْمِذِيّ وَأَبُو دَاوُد
Original Reference: Mishkat al-Masabih 522