The Fifth Pillar of Islam is the Hajj, which is an annual pilgrimage to Mecca that all Muslims are expected to make at least once in their lifetime. The Hajj is a religious duty that must be performed by all able-bodied Muslims who can afford it. The Hajj is also known as Hadj (4 letters) or Haj (3 letters). During the Hajj, pilgrims perform a series of rituals, including circling the Kaaba seven times, running between two hills, and throwing stones at pillars representing the devil. The Hajj is a powerful symbol of unity among Muslims and is one of the most important religious observances in Islam.