Islam (/ˈɪslɑːm/;Arabic: الإسلام, IPA: [alʔisˈlaːm]) is an Abrahamic monotheistic religion which professes that there is only one and incomparable God (Allah) and that Muhammad is the last messenger of God. It is the world's second-largest religion and the fastest-growing major religion in the world, with over 1.7 billion followers or 23% of the global population, known as Muslims. Islam teaches that God is merciful, all-powerful, and unique; and He has guided mankind through revealed scriptures, natural signs, and a line of prophets sealed by Muhammad. The primary scriptures of Islam are the Quran, viewed by Muslims as the word of God, and the teachings and normative example (called the sunnah, composed of accounts called hadith) of Muhammad (c. 570–8 June 632 CE). The cities of Mecca, Medina and Jerusalem are home to the three holiest sites in Islam.