Narrated Abu Huraira رضي الله عنه (May Allah be pleased with him): The Prophet صلى الله عليه وسلم (Peace be upon him) said, "Allah says, I will be against three persons on the Day of Resurrection:(one of them is ): One who sells a free person (as a slave) and eats the price.

[Sahi Bukhari, Hadith no. 2227]