Proclaiming One unifying religion for all the people. The Book is, without a doubt, a revelation from the Lord of the Universe. The Final Testament comes with built-in physical evidence that it is God's message to you; it is mathematically composed beyond human capability.

This proves that God is the Truth, and that He revives the dead, and that He is Omnipotent. 

Our Salvation in the hereafter lies on upholding The Quran. The Quran is God's Final Testament to the world. Unlike any other book, the Quran is taught by God (55:1-2); He teaches us what we need at the time we need it. This is why we read the Quran hundreds of times without getting bored. We can read a novel, for example, only once. But the Quran can be read an infinite number of times, and we derive new and valuable information from it every time.

Since the Quran is God's message to all the people, regardless of their language, the Quran is accessible to the believers, regardless of their language (41:44). 

This explains a profound phenomenon: the believers who do not know Arabic know the Quran better than the Arabic speaking unbelievers. Because of the invisible forces serving the Quran, it is readily and enjoyably accessible to the sincere believers, and utterly inaccessible to the unbelievers (17:45, 18:57, 56:79).