The following question was posed to Shaikh Bin Baz: “Some people get a mus’haf and look into it [reading in the mind] without moving their lips; is it still applicable to term this scenario as “reading the Qur’an”? Or is it a must to pronounce/utter the words and for that to be heard in order to deserve the reward for reading the Qur’an? And is a person rewarded for just looking into a mus’haf [reading in mind]?
There is nothing preventing looking into the Qur’an without reading [physically] to ponder and contemplate and understand the meanings, but the one who does this is not considered “a reader” [to have actually ‘read’ the Qur’an] and he does not receive the virtue of actually reading unless he pronounces the words and physically reads the Qur’an, even if those around him cannot hear [i.e. it is not required to be loud, but physical pronunciation required though], due to the statement of the prophet “Read the Qur’an for indeed it will come as an Intercessor for its companions on the Day of Judgement” [Muslim]. The prophet صلى الله عليه و سلم intended by the ‘companions of it’ i.e. those who act upon it, just as it is mentioned in other ahaadith.
Similarly the prophet صلى الله عليه و سلم said, “Whoever reads a letter of the Qur’an so for him is a reward, and every reward is 10-fold of its example” [at-Tirmidhy & ad-Daarimy with an authentic chain]. And a person is not considered a “reader” unless he utters [and pronounces that reading], just as the people of knowledge have stated that.
[Paraphrased from official website of Shaikh Bin Baz http://www.binbaz.org.sa/mat/2013]