If religion were based on personal opinion, the bottom of the leather sock would be more deserving of being wiped than the top. Yet I saw the Messenger of Allah ﷺ wipe over the upper surface of his leather socks.
حدثنا محمد بن العلاء حدثنا حفص يعني ابن غياث عن الأعمش عن أبي إسحق عن عبد خير
لو كان الدين بالرأي لكان أسفل الخف أولى بالمسح من أعلاه وقد رأيت رسول الله ﷺ يمسح على ظاهر خفيه
Its isnad is daif. Daraqutni reported it in 1/98, hadith 759, from the hadith of Hafs bin Ghiyath, and Yazid bin Abdul-Aziz, Isa bin Yunus and Waki also transmitted it following him. See Musnad Imam Ahmad with its supplementary additions, 1/95, 114, 124. Abu Ishaq used an ambiguous form of transmission (anana), but the hadith of Humaydi, no. 47, suffices in its place.