Tafseer Ibn Kathir : 56. Al-Waqi’ah
(7. And you (all) will be in three groups. )
(8. So those on the right — how (fortunate) will be those on the right!)
(9. And those on the left — how (unfortunate) will be those on the left!)
(10. And those foremost will be foremost.)
(And you (all) will be in three groups.) This means that people will be divided into three categories on the Day of Resurrection.
Some will on the right of Allah’s Throne, and they are those who were brought forth from `Adam’s right side. This category will be given their Books of Records in their right hand and will be taken to the right side. As-Suddi explained that they will comprise the majority of the residents of Paradise.
Another category is those who will be placed to the left of Allah’s Throne, and they are those who were brought forth from `Adam’s left side. This category will be given their Books of Records in their left hands and will be taken to the left side. They are the residents of the Fire, may Allah save us from their actions.
A third category is comprised of those who are the foremost and nearest before Allah. They are in a better grade and status and nearer to Allah than those on the right side. They are the chiefs of those on the right side, because they include the Messengers, Prophets, true believers and martyrs. They are fewer than those on the right side;
so Allah said,
(So those on the right — how will be those on the right! And those on the left — how will be those on the left! And those foremost will be foremost.) Allah divides people into these three groups upon their death, as indicated by the end of this Surah. Allah mentioned them in His statement as well,
(Then We gave the Book as inheritance to such of Our servants whom We chose. Then of them are some who wrong themselves, 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.)(35:32) Muhammad bin Ka`b, Abu Hazrah Ya`qub bin Mujahid said that,
(And those foremost will be foremost.) is about the Prophets, peace be upon them, while As-Suddi said that they are the residents of the utmost highs (Ahl Al-`Illiyyin, in Paradise). The meaning of foremost is that they were foremost in performing the acts of righteousness just as Allah commanded them,
(And march forth in the way to forgiveness from your Lord, and for Paradise as wide as the heavens and the earth.)(3:133) and,
(Race with one another in hastening towards forgiveness from your Lord, and Paradise the width whereof is as the width of the heaven and the earth.)(57:21) Therefore, those who rush to obey Allah in this life and are foremost in performing acts of righteousness, will be among the foremost believers honored in the Hereafter. Verily, the reward is according to the kind of deed, and as one does, so he is judged. So Allah said:
(These will be the nearest (to Allah). In the Gardens of Delight.)
Source : Quran : Tafsir Ibn Kathir : Surah No.56 : Three Categories of People on the Day of Resurrection