Thumma awrathna alkitaba allatheena istafayna min AAibadina faminhum thalimun linafsihi waminhum muqtasidun (surah Fatir: 32)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(35:32) Then We bequeathed the Book to those of Our servants that We chose. *55Now, 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. *56

Summa awrasnal Kitaaballazeenas tafainaa min `ibaadinaa faminhum zaalimul linafsihee wa minhum muqtasid, wa minhum saabiqum bilkhairaati bi iznil laah; zaalika huwal fadlul kabeer

*55) This implies the Muslims, who have been sorted out from all mankind so that they may become heirs to the Book of Allah, and convey its message to others after the Holy Prophet Muhammad (upon whom be Allah's peace and blessings). Though this Book has been presented before all human beings, those who accepted it in the first instance, were chosen for the honour to become heirs to a great Book like the Qur'an and the trustees of the teaching and guidance imparted by a great Messenger like the Holy Prophet Muhammad (upon whom be Allah's peace and blessings).
*56) That is, "All these Muslims are not alike but are divided into three classes: (1) Those unjust to themselves: They are those who believe sincerely and honestly that the Qur'an is the . Book of Allah and Muhammad (upon whom be Allah's peace) the Messenger of Allah, but in practical life do not fully follow the Book of Allah and the Sunnah of His Messenger. They are believers but sinful; culprits but not rebellious; weak of faith but not hypocritical and unbelieving at heart. Therefore, although they are 'unjust to themselves," they have been included among the chosen servants of God and among the heirs to the Book; otherwise, obviously the rebels and the hypocrites and the unbelieving people could not be so treated and honoured. This class of the believers have been mentioned first of All because they are most numerous among the Muslims.
(2) Those following the middle course: They are the people who fulfil the obligations of this inheritance to some extent but not fully. They are obedient as well as erring. They have not left their self altogether free but try as best as they can to turn it to God's obedience; however, at times they give it undue freedom and become involved in sin. Thus, their life becomes a combination of both the good and the evil actions. They are less numerous than the first group but more than the third; that is why they have been mentioned second.
(3) Those excelling in good deeds: They are the people of the first rank among the heirs to the Book, and they are the ones who are doing full justice to the inheritance. They are in the forefront in following and adhering to the Book and the Sunnah; in conveying the message of God to His servants, in offering the sacrifices for the sake of the true Faith, and in every pious and good work. They arc not the ones who would commit a sin deliberately, but if they happened to commit a sin inadvertently, they would be filled with remorse as soon as they became conscious of it. They are less numerous than the people of the first two groups, and therefore, have been mentioned last, although they merit the first place in the matter of doing justice to the heritage of the Book of Allah
As for the sentence, "this is the supreme bounty', if it is related with the last sentence, it would mean that to excel in good deeds is the supreme bounty, and the people who excel in good deeds are the best of the Muslim community. And if it is taken to be related with the first sentence, it would mean that to be a heir to the Book of Allah and to be chosen for this heritage is the supreme bounty, and the people who have been so chosen on account of their faith in the Qur'an and the Holy Prophet Muhammad arc the best among the human beings created by Allah.