Allah tells us that His Awliya' (friends and allies) are those who believe and have Taqwa of Allah as He defined them. Every pious, God-fearing person is a friend of Allah, therefore,

[لاَ خَوْفٌ عَلَيْهِمْ]

(no fear shall come upon them) from the future horrors they will face in the Hereafter.

[وَلاَ هُمْ يَحْزَنُونَ]

(nor shall they grieve.) over anything left behind in this world. Ibn Jarir recorded that Abu Hurayrah said that Allah's Messenger said:

«إِنَّ مِنْ عِبَادِ اللهِ عِبَادًا يَغْبِطُهُمُ الْأَنْبِيَاءُ وَالشُّهَدَاء»

(Among the servants of Allah there will be those whom the Prophets and the martyrs will consider fortunate). It was said: "Who are these, O Messenger of Allah, so we may love them'' He said:

«هُمْ قَوْمٌ تَحَابُّوا فِي اللهِ مِنْ غَيْرِ أَمْوَالٍ وَلَا أَنْسَابٍ، وُجُوهُهُمْ نُورٌ عَلَى مَنَابِرَ مِنْ نُورٍ، لَا يَخَافُون إِذَا خَافَ النَّاسُ، وَلَا يَحْزَنُونَ إِذَا حَزِنَ النَّاس»

(These are people who loved one another for the sake of Allah without any other interest like money or kinship. Their faces will be light, upon platforms of light. They shall have no fear (on that Day) when fear shall come upon people. Nor shall they grieve when others grieve.) Then he recited:

[أَلا إِنَّ أَوْلِيَآءَ اللَّهِ لاَ خَوْفٌ عَلَيْهِمْ وَلاَ هُمْ يَحْزَنُونَ ]

(Behold!! Verily, the Awliya' (friends and allies) of Allah, no fear shall come upon them nor shall they grieve.)