Surah 4. An-Nisaa', Ayah 59

I.e., to the Qur'an and to the sunnah (the sayings and the practice) of the Prophet. See also verse {65} of this surah.

Read in conjunction with 3:26 , which speaks of God as "the Lord of all dominion" - and therefore the ultimate source of all moral and political authority - the above passage lays down a fundamental rule of conduct for the individual believer as well as the conceptual basis for the conduct of the Islamic state. Political power is held in trust (amanah) from God; and His will, as manifested in the ordinances comprising the Law of Islam, is the real source of all sovereignty. The stress, in this context, on "those from among you who have been entrusted with authority" makes it clear that the holders of authority (ulu 'l-amr) in an Islamic state must be Muslims.

I.e., from among the believers.

Ulu-l-amr = those charged with authority or responsibility or decision, or the settlement of affairs. All ultimate authority rests in Allah. Prophets of Allah derive their authority from Him. As Islam makes no sharp division between sacred and secular affairs, it expects governments to be imbued with righteousness. Likewise Islam expects Muslims to respect the authority of such government for otherwise there can be no order or discipline.