Though I have limited time at my disposal, a quick response is in order. Syed bhai, don't raise such questions, for such questions expose the outside notions being brought to bear on Quran. To your question, brother Jawaid has quoted 2:170-171. You must have noticed, br. Jawaid neglected the context mentioned in 2:168 as well as 2:172, which make absolutely clear as to what is being referred here. He then goes on to advise you to go back some verses preceding 13:17, but he neglected the same in 2:170 as I mentioned above. This should explain the problem one faces when one tries to see what Quran is stating over and over again at various places (for example Salat) and what some quran-only-banner carriers want you to believe through selective reading.