In surah an-Nur, Allah (Most High) promises the believers that He will certainly establish them in the land لَيَسْتَخْلِفَنَّهُمْ, which is good news promising the establishment of a Khilafah which will implement Islam and change the fear Muslims are living in nowadays to one of security. Allah (Most High) says:
وَعَدَ اللَّهُ الَّذِينَ آمَنُوا مِنْكُمْ وَعَمِلُوا الصَّالِحَاتِ لَيَسْتَخْلِفَنَّهُمْ فِي الْأَرْضِ كَمَا اسْتَخْلَفَ الَّذِينَ مِنْ قَبْلِهِمْ وَلَيُمَكِّنَنَّ لَهُمْ دِينَهُمُ الَّذِي ارْتَضَىٰ لَهُمْ وَلَيُبَدِّلَنَّهُمْ مِنْ بَعْدِ خَوْفِهِمْ أَمْنًا ۚ يَعْبُدُونَنِي لَا يُشْرِكُونَ بِي شَيْئًا ۚ وَمَنْ كَفَرَ بَعْدَ ذَٰلِكَ فَأُولَٰئِكَ هُمُ الْفَاسِقُونَ
“Allah has promised those of you who have iman and do righteous actions that He will make them successors in the land as He made those before them successors, and will firmly establish for them their deen with which He is pleased and give them, in place of their fear, security. ‘They worship Me, not associating anything with Me.’ Any who are kafir after that, such people are deviators.” (An-Nur, 55)
But what are the “righteous actions”? Are these simply individual acts of ibadah such as praying and fasting as some have focused on?
Tabari in his tafseer answers this question very succinctly:
وأطاعوا الله ورسوله فيما أمراه ونهياه
“They obey Allah and His Messenger in whatever He commands and forbids.”
This links back to the previous verse which begins, قُلْ أَطِيعُوا اللَّهَ وَأَطِيعُوا الرَّسُولَ “Say: ‘Obey Allah and obey the Messenger.” (An-Nur, 54)
Therefore, the ummah has a responsibility to obey all the commands of Allah which includes the work to re-establish the Khilafah which is at the head of the duties of sufficiency (fard al-Kifiyah), because so many duties depend upon it including the peak of Islam, jihad.