The minimum that a Muslim must do and believe in order to be assured of their salvation is quite simple. They must "Worship God (Allah) without worshiping anything along with Him, offer the (five daily) prescribed prayers, pay the compulsory alms, and fast the month of Ramadan." Islam is based upon five pillars:
Shahada: bearing witness that there is nothing worthy of worship by God and that Muhammad is God's messenger
Salat: performing the prescribed Islamic prayer
Zakat: giving of a 2 1/2 % tax on one's assets
Sawm: fasting from sunrise to sunset during the month of Ramadan, and
Hajj: performing the pilgrimage to Mecca
Over the course of a few centuries the ways in which the Islamic principles have been interpreted in the form of the four major Sunni "schools of law" in addition to the Shi'i schools, the most dominant of which is the Ithna 'Ashari or Ja'fari madhhab. Sunni Muslims are the largest group in Islam. The Sunnah (the example of Muhammad's life) as recorded in the Qur'an and the hadith is the main pillar of Sunni doctrine. Sunnis recognize four major legal traditions: Hanafi, Maliki, Shafii'i, and Hanbali. The Shi'i believe in the political and religious leadership of infallible Imams. They believe that he, as the cousin and son-in-law of Muhammad, was his rightful successor, and they call him the first Imam (leader), rejecting the legitimacy of the previous Muslim caliphs. An Imam rules by right of divine appointment and holds "absolute spiritual authority" among Muslims, having final say in matters of doctrine and revelation. The two branches disagree over the proper importance and validity of specific collections of hadith.
Muhammad ibn 'Abd was the founder of the world religion of Islam and is regarded by Muslims as the last messenger and prophet of God. Muslims consider him the restorer of the original faith of Adam, Abraham and others. The most credible source of information for the life of Muhammad is the Qur'an. The Qur'an refers to Muhammad as "a mercy to the worlds." Islam forbids visual depictions of Muhammad. This tradition it held stronger by Sunni Islams. Muhammad's birthday is celebrated as a major feast throughout the Islamic world. In these celebrations, Muslims remember the miracles associated with Muhammad's life. When Muslims say or write the name of Muhammad or any other Muslim prophet, they usually follow it with Peace by upon him or its Arabic equivalent, sallalahu alayhi.