Hadith 3:223
‘Ali said, “If the religion were based on opinion, it would be more important to wipe the under part of the shoe than the upper, but I have seen God’s messenger wiping over the upper part of his shoes.” Abu Dawud transmitted it, and Darimi has something similar.
وَعَن عَليّ رَضِي الله عَنهُ قَالَ: لَوْ كَانَ الدِّينُ بِالرَّأْيِ لَكَانَ أَسْفَلُ الْخُفِّ أَوْلَى بِالْمَسْحِ مِنْ أَعْلَاهُ وَقَدْ رَأَيْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَمْسَحُ على ظَاهر خفيه رَوَاهُ أَبُو دَاوُد للدارمي مَعْنَاهُ
Original Reference: Mishkat al-Masabih 525