Wiping over khuff during ablution is a form of Islam easiness when it is hard to remove it or its likes. But some conditions make it invalid like; time limit and feet exposure. More cases are clarified in this article.

Wiping over the kuffs is permitted instead of removing it during ablution. The Prophet (PBUH) used to wipe over the top of his khuffs, and if one wipes over the back or the bottom of his khuffs; wiping is invalid.  

Instead of removing your socks or khuffs during each ablution, one can wipe over it. But there are some conditions and rules to be followed so the wiping is valid. This article discusses these conditions in details.

When a husband swears not to have sexual intercourse with his wife forever or for more than four months this is Ila’ and it is forbidden. If he doesn’t atone for his oath within this period the case must be put to a judge.