Abu Dawud
Prayer
Book Number: 002 / Hadith Number: 593
Narated By Abdullah ibn Umar : The Prophet (pbuh) said: There are three types of people whose prayer is not accepted by Allah: One who goes in front of people when they do not like him; a man who comes dibaran, which means that he comes to it too late; and a man who takes into slavery an emancipated male or female slave.