Sayyiduna Ibn Abbas (may Allah be pleased with them both) said concerning this saying of Allah Almighty, "Indeed, they do not deny you" [Al-An'am: 33], which he (Ibn Abbas) used to recite with the lighter reading: "They are not able to make it so that (you) are not a Messenger, nor are they able to make it so that the Qur'an is not the Qur'an. Yes, they deny you with their tongues, so they deny you (verbally), and this is nothing but denial, and that is the denial (meant)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12604