so Allah said,

فَأَصْحَابُ الْمَيْمَنَةِ مَا أَصْحَابُ الْمَيْمَنَةِ ﴿٨﴾

وَأَصْحَابُ الْمَشْأَمَةِ مَا أَصْحَابُ الْمَشْأَمَةِ ﴿٩﴾

وَالسَّابِقُونَ السَّابِقُونَ ﴿١٠﴾

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,

ثُمَّ أَوْرَثْنَا الْكِتَـبَ الَّذِينَ اصْطَفَيْنَا مِنْ عِبَادِنَا فَمِنْهُمْ ظَـلِمٌ لِّنَفْسِهِ وَمِنْهُمْ مُّقْتَصِدٌ وَمِنْهُمْ سَابِقٌ بِالْخَيْرَتِ بِإِذُنِ اللَّهِ

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, وَالسَّابِقُونَ السَّابِقُونَ (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,

وَسَارِعُواْ إِلَى مَغْفِرَةٍ مِّن رَّبِّكُمْ وَجَنَّةٍ عَرْضُهَا السَّمَـوَتُ وَالاٌّرْضُ

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,

سَابِقُواْ إِلَى مَغْفِرَةٍ مِّن رَّبِّكُمْ وَجَنَّةٍ عَرْضُهَا كَعَرْضِ السَّمَآءِ وَالاٌّرْضِ

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.