The number one pillar of Islam is Iman, which means faith or belief. It is the belief in the oneness of God (Allah) and that Prophet Muhammad is the messenger of God. This belief is the foundation of Islam and is a requirement for any individual to become a Muslim. Iman also includes the belief in the angels, the holy books (such as the Quran), the Day of Judgment, and divine decree. It is the first and most important of the Five Pillars of Islam, which are the basic acts of worship that are central to the practice of Islam. Without Iman, a Muslim's actions, such as prayer, charity, fasting, and pilgrimage, would not have any spiritual significance.