"Abu Hurairah (May Allah be pleased with him) reported:
The Prophet () said, ""Allah, the Exalted, says: 'I will contend on the Day of Resurrection against three (types of) people: One who makes a covenant in My Name and then breaks it; one who sells a free man as a slave and devours his price; and one who hires a workman and having taken full work from him, does not pay him his wages.""'

[Al Bukhari]."