Tirmidhi, in his Nawadir Al-Usul, said: The Glorious Qur’an is sacred so that one can not even touch it without being pure and safe from filth. The same is applicable upon starting to recite it. Moreover, one should use the siwak (tooth-stick) to clean and purify his mouth, as it is the way the Qur’an takes. Yazeed Ibn Abu Malik said: Your mouths are a way taken by the Glorious Qur’an, so, clean and purify them as much as you can.