“Not everyone is capable of carrying out the actions necessary to enjoin right conduct. However, this can be performed effectively by the ruler [Sultan] because he holds the authority to frame laws that will be in accord with the Shari‘ah. As ruler, he has the final word in matters of consequence, such as the legislation of laws, the prosecution of punishable offences and the treatment of prisoners. The role of head of state must be entrusted to an honest, strict, and righteous person since he holds the responsibility of enforcing the dictates of the Shari‘ah in all matters. It is incumbent on the ruler to appoint suitable, powerful and just persons in every city for this purpose. This is because Allah says, “[They are] those who, if We give them power in the land, establish [regular] prayer and give [regular] charity, enjoin right and forbid wrong; with Allah rests the end [and decision] of [all] affairs.” (22:41)”
[Imam al-Qurtubi, الجامع لأحكام القرآن, vol. 4, p. 47. Translated by Syed Amin Ashraf in Ma‘roof & Munkar, Jalaluddin Umari, International Islamic Publishing House, Riyadh, 2008 (2nd Revised Edition), p. 119]
Imam al-Qurtubi is Muhammad ibn Ahmad ibn Abu Bakr ibn Farah, Abu ‘Abdullah al-Ansari al-Qurtubi, of Cordova (in present-day Spain). A Maliki scholar and hadith specialist, he was one of the greatest Imams of Qur’anic exegesis, an ascetic who divided his days between worship and writing. Educated in hadith by masters like ‘Ali ibn Muhammad al-Yahsabi and al-Hasan ibn Muhammad al-Bakri, we wrote works in the sciences of hadith and tenets of faith, though his enduring contribution is his al-Jami‘ li ahkam al-Qur’an (The Compendium of the Rules of the Qur’an), from which he mainly omitted the stories and histories customary in other commentaries, and recorded instead the legal rulings contained in the Qur’an and how scholars have inferred them, together with the usage of Arabic grammar. Scholars have used it extensively ever since it was written. It is related that Qurtubi disdained airs, and used to walk about in a simple caftan with a plain cap (taqiyya) on his head. He travelled east and settled in Munya Abi al-Khusayb in upper Egypt, where he died in 671H (1273 CE) [Excerpted from Reliance of the Traveller by Shaykh Nuh Keller, p. 1090]
The Caliphate 