Praise be to Allah.and blessings and peace be upon the Messenger of Allaah.
If he takes off his leather slippers (khufoof) or socks after wiping over them that does not invalidate his wudoo’, according to the correct scholarly view, because when a person wipes over his socks, he has completed his wudoo’ according to what is implied by the shar’i evidence. So if he takes them off, this wudoo’ is still valid according to the shar’i evidence and cannot be broken except by something for which there is shar’i evidence. There is no evidence to indicate that taking off leather slippers or socks that have been wiped invalidates wudoo’. On this basis, then, his wudoo’ remains valid. This was the view favoured by Shaykh al-Islam Ibn Taymiyah and a group of the scholars. But if he puts his socks back on after that and breaks his wudoo’, then he wants to wipe over them again, that is not allowed, because he has to put the socks on after doing wudoo’ in which he washed his feet, according to what was stated by the scholars. And Allaah knows best.