Shaykh Muhammad al-Ameen al-Shanqeeti mentioned in his book Adhwaa’ al-Bayaan that from amongst the verses that give the most hope to a believer is:
“Then We gave the Book (the Quran) for inheritance to such of Our slaves whom We chose. Then of them are some who wrong their ownselves, and of them are some who follow a middle course, and of them are some who are, by Allah’s Leave, foremost in good deeds. That (inheritance of the Quran), that is indeed a great grace.” [al-Faatir: 32]
Allaah `azza wa jall makes it clear in this verse that the Ummah’s inheritance of the Book of Allaah is an indication that He subhaanahu wa ta’aala has chosen it above others, “Then We gave the Book (the Quran) for inheritance to such of Our slaves whom We chose”
Then He clarified that they were of three groups.
First: The dhaalim li-nafsihi – the one who oppresses and wrongs himself, he obeys Allaah and disobeys Him at times. About such a person, Allaah `azza wa jall has said
“…they have mixed a deed that was righteous with another that was evil. Perhaps Allah will turn unto them in forgiveness…” [al-Tawbah: 102]
Second: The muqtasid – the one who takes a middle path. He is the one that obeys Allaah and does not disobey Him, but yet he doesn’t draw closer to Him by the nawaafil (supererogatory deeds)
Third: The saabiq bil-khayraat – the one who races to do righteous deeds and he is the one that performs the obligatory and avoids the muharramaat (forbidden acts) and he draws closer to Allaah with acts of obedience that are otherwise not mandatory.
And this is the most correct interpretation regarding the 3 types of people in this verse.
Then Allaah subhaanahu wa ta’aala promised all three of them everlasting Paradise as the next verse says:
“‘Adn (Eden) Paradise will they enter, therein will they be adorned with bracelets of gold and pearls, and their garments there will be of silk…” [al-Faatir: 33]
This is where the importance of grammer comes in because the only way it is understood that all 3 types of the above people in this Ummah will enter Paradise is due to the letter waaw (و) in the word يدخلونها. This is called the waaw al-jam’ and it represents the action of 3 or more people, e.g:
يدخل – He enters
يدخلان – They (2 people only) enter
يدخلون – They (pl. 3 or more) enter
This is why some people say regarding the waaw in the above ayah: “حق لهذه الواو أن تكتب بماء العينين” – i.e. ‘this waaw has a right to be written with teardrops.’ And the fact that the first of the 3 types to be mentioned is the one who wrongs himself, brings the most hope to such a person in this Ummah.
The people of knowledge differed as to why the dhaalim li-nafsihi (the one who wrongs himself) was mentioned prior to the the muqtasid (one taking a middle path) and the saabiq (one racing in good). Some of them said that the dhaalim was mentioned first so that he doesn’t despair and the saabiq was mentioned last so that he doesn’t become amazed at his deeds, rendering them vain.
Others said that the dhaalim was preceded first because most of the people in Jannah are those who have wronged themselves and the ones who do not fall into disobedience are very few as is stated in the ayah:
“…except those who believe and do righteous good deeds, and they are few….” [Saad: 24]
Info from: أضواء البيان في إيضاح القرآن بالقرآن – by Shaykh Muhammad al-Ameen al-Shanqeeti.