Sahih Al Bukhari – Book of Hiring

Volumn 003, Book 036, Hadith Number 470. 
—————————————– 
Narated By Abu Huraira RA : The Prophet PBUH said, "Allah said, 'I will be an opponent to three types of people on the Day of Resurrection: 

1. One who makes a covenant in My Name, but proves treacherous. 
2. One who sells a free person and eats his price. 
3. One who employs a laborer and takes full work from him but does not pay him for his labour.'" 

Covenant means: an agreement, usually formal, between two or more persons to do or not dosomething specified.

treacherous means: unfaithful, faithless, treasonous. 2.  deceitful. (dhoka)

—