Abd Khayr reported,
I saw Ali 
perform ablution. He washed the tops of his feet and said, "Had I not seen the Messenger of Allah ﷺ wash the tops of his feet, I would have thought that the bottoms were more deserving of being washed."
Ahmad 918
Sahihحدثنا عبد الله حدثنا إسحاق بن إسماعيل حدثنا سفيان عن أبي السوداء
عن ابن عبد خير عن أبيه قال
رأيت عليا رضي الله عنه توضأ فغسل ظهر قدميه وقال لولا أني رأيت رسول الله ﷺ يغسل ظهور قدميه لظننت أن بطونهما أحق بالغسل
Its chain of transmission is sahih. Abu Sawda is Amr bin Imran Hindi Kufi, whom Ahmad and Ibn Main deemed trustworthy, and Ibn Hibban mentioned him in Thiqat. Ibn Abd Khayr is Musayab bin Abd Khayr, whom Ibn Main deemed trustworthy, and Ibn Hibban mentioned him in Thiqat. Bukhari gave his biography in Kabir 4/1/408 without mentioning any criticism of him.Abu Dawud referred to the hadith in a suspended form, saying, "Abu Sawda also narrated it," and so on. The commentator on Awn al-Mabud noted that this is the narration of Lului, and that the narration of Ibn Dasah is a connected one, and he mentioned its chain of transmission.See what came before this, and see also 1014 and 1015.