[Pooya/Ali Commentary 14:16] Aqa Mahdi Puya says: The hell will be in front of the evil-doers, but as they never look forward-they are involved in the immediate past or the present-the Quran uses wara which literally means "behind", because from the standpoint of application of the heart and mind their future is always behind them. For "a festering or putrid water" see commentary of al Kahf: 29 and Muhammad: 15.