Taken from Al-Maqasid : Imam Nawawi's Manual of Islam1
1.1 The first obligation of all who are morally responsible (Arabic: mukallaf, someone who has reached the age of puberty and is of sound mind) is to know God, meaning know that He is existent and not nonexistent; beginninglessly eternal, not originating in or subject to time or space; everlastingly abiding, not subject to end; dissimilar to and other than anything within time or space, nothing in any way resembling Him; self-subsistent, free of need for anything through which to exist or any determinant to condition Him; One, without co-sharer in His entity, attributes, or actions; possessed of almighty power, will, knowledge, life, hearing, sight, speech, such that He is almighty, and wills, knows, lives, hears, sees, and speaks.
1.2 He sent the prophets out of His generosity, protecting them from everything unbecoming them, guarding them from both lesser sins and enormities both before their prophethood and thereafter, and from every offensive physical trait such as leprosy or blindness, though they ate, drank and married. They were the best of all created beings; and the highest of them was him whom Allah chose to be the final seal of prophethood, whose Sacred Law superseded all previously valid religious laws, our prophet Muhammad (Allah bless him and give him peace). His Companions (Sahaba) were the finest generation, the best of them being Abu Bakr, then 'Umar, then 'Uthman, then 'Ali, may the benefaction of Allah be upon them all.
1.3 We believe in everything that Allah has informed us of upon the tongue of Muhammad (Allah bless him and give him peace), such as angels, the sacred scriptures, the questioning of the dead in their graves about their faith, the resurrection of the dead, their being gathered unto the Judgment Day, the terror of it, the taking of the pages in which one's good deeds and bad deeds are recorded, the weighing of them, the balance scales, the high, narrow bridge over the hellfire that the saved will pass over to paradise, the intercession of the prophets and righteous for others, and in paradise and hell.
1.4 Everything that is necessarily known by Muslims to be of the religion (necessarily known meaning the things that any Muslim would know about if asked) is obligatory to believe, and anyone who denies it is a non-Muslim (unless he is a recent convert or was born and raised in the wilderness or for some similar reason has been unable to learn his religion properly. Muslims in such a condition should be informed about the truth, and if they then continue as before, they are adjudged non-Muslims as is also the case with any Muslim who believes it permissible to commit adultery, drink wine, kill without right, or do other acts that are necessarily known to be unlawful).”
1 Nawawi, Yahya ibn Sharaf. Al-Maqasid : Imam Nawawi's Manual of Islam. 1st ed. Trans. and appendices Noah Ha Mim Keller. Evanston: Sunna Books, 1994.