Allaah سبحانه و تعالى says,
"We have indeed sent down signs that make things clear. And Allaah guides whom He wills to a path that is straight." (Sooratun-Noor, 24:46)
The clear signs have come from Allaah سبحانه و تعالى. However, the one who reads the Qur'aan must realise that its guidance will only come to him if Allaah سبحانه و تعالى wills it so. Guidance is in the hand of Allaah سبحانه و تعالى and He gives it to whomsoever He wills, according to His divine justice and mercy. This fact must be very clear in everyone's heart. The reader must turn to Allaah سبحانه و تعالى while reading the Qur'aan realising that the benefits of the Qur'aan will only come because of his sincerity to Allaah سبحانه و تعالى.
[How to Approach and Understand the Quran, p. 112]