Importance of Making Wudhu Thoroughly

عن أبي هريرة رضي الله عنه أن النبي صلى الله عليه وسلم رأى رجلا لم يغسل عقبيه فقال ويل للأعقاب من النار (الترغيب والترهيب 1/234)

Hazrat Abu Hurayrah (radhiyallahu ‘anhu) reports that Rasulullah (sallallahu ‘alaihi wasallam) once saw a person making wudhu and he did not wash his heels. Rasulullah (sallallahu ‘alaihi wasallam) said: “Doom and destruction in the fire is for the (one who during wudhu does not wash his) heels.”