Allah has obliged on his slaves entering islam and warned them from things contradicting it.And he sent His messenger to call to these and He told us that the one who follows him is guided to the right and the one who turns away from His orders has gone astray.And in lot of ayahs He warned us of apostasy,disbelief and polytheism.The
person may apostatize from his religion
by a lot of contradictions which make his
blood and money lawful and is considered as an apostate