Fatir (The Creator) - Chapter 35: Verse 32
"Then we bequeathed the Book to those of Our servants that We chose. Now, some of them wrong themselves and some follow the medium course; and some, by Allah's leave, vie with each other in acts of goodness. That is the great bounty."
The Book of God, the Quran, was presented before all mankind and those who stepped forward and accepted it (the Muslims) were chosen to become its standard-bearers after the Prophet, peace be upon him.
These Muslims, however, are not all alike; rather, they belong to the following three categories:
1. "Those who wrong themselves". These Muslims sincerely believe in the Quran as God's Book and in Muhammad as God's Messenger. However, in their practical lives they fail to follow the Book of God and the way of His Prophet to the extent they should. Despite being believers they still commit sin. While such people might be iniquitous, they are not rebels. Their belief might be a bit feeble, yet they are neither hypocrites nor wilful unbelievers. In recognition of this, the Quran brands them as God's chosen servants to whom His Book has been bequeathed. Among the believers of all the three categories, they are the first to be mentioned for they constitute the majority of Muslims.
2. Then comes those "who follow the medium course". That is, they are the ones who fulfil, though partially, the requirements ensuing from the bequest of God's book on them. They represent a mixture of obedience and disobedience. Such people, however, do not give an altogether free rein to their desires; rather, they try to control them. Nevertheless, at times they let their desires loose a bit which leads to sinful behaviour. Such people are less in number than the people of the first category but outnumber those of the third category mentioned below.
3. Then comes those "who view with one another in acts of goodness". Among the believers, they occupy the forefront. They stand out as the true trustees of the Book of God. They outstrip others as they are exceedingly active in following the Book of God and the way of the Prophet, in communicating God's Message to His servants, in offering sacrifices for the cause of faith, and in doing acts of goodness. They are not the ones who would deliberately commit a sin; but if they happen to fall into sin, they repent as soon as they realise this. In number, these are less than the two groups mentioned above. Although they are mentioned after those groups, they are in fact well ahead of them in acquitting themselves of the trusteeship of the Quran.
"Towards Understanding the Quran" - Sayyid Abul Ala Mawdudi, Vol. 9, pp. 228-230