Sahih Bukhari Volume 3, Book 34, Hadith Number 430.

Narated By Abu Huraira : The Prophet said, “Allah says, ‘I will be against three persons on the Day of Resurrection:

1. One who makes a covenant in My Name, but he proves treacherous.
2. One who sells a free person (as a slave) and eats the price.
3. And one who employs a laborer and gets the full work done by him but does not pay him his wages.'”