Abu Hurairah (Ra) narrates that Rasúlullãh (saw) said: The world is a believer's prison, and an unbeliever's Paradise.
(Muslim)

Note: For a believer the rewards and delights of Paradise which are there for him make this world like a prison; and for the unbeliever, -there is endless Punishment in the Hereafter and so this world is for him like Paradise. (Mirqãt)