Surah Al Fussilat

The disbelievers had given clear notice to the Prophet to the effect, "You may continue your mission of inviting the people to yourself, but we will go on opposing you as hard as we can to frustrate your mission." To accomplish this objective they had devised a plan that whenever the Prophet or one of his followers would try to recite The Qur'an before the people, they would at once make so much noise that no one could hear anything.
In response to this, this Surah has clearly stated: "This Qur'an is an unchangeable Book and you can not defeat it by your noise and falsehoods. Whether falsehood comes from the front or makes a secret and indirect attack from behind, it cannot succeed in refuting it. Now that the Qur'an is being presented in your own language so that you may understand it, you say that it should have been revealed in some foreign language.