The qibla () is the direction towards the Kaaba in the Sacred Mosque in Mecca, which is used by Muslims in various religious contexts, particularly the direction of prayer for the salah. In Islam, the Kaaba is believed to be a sacred site built by prophets Abraham and Ishmael, and that its use as the qibla was ordained by Allah in several verses of the Quran revealed to Muhammad in the second Hijri year. Prior to this revelation, Muhammad and his followers in Medina faced Jerusalem for prayers. Most mosques contain a mihrab (a wall niche) that indicates the direction of the qibla. The qibla is also the direction for entering the ihram (sacred state for the hajj pilgrimage); the direction to which animals are turned during dhabihah (Islamic slaughter); the recommended direction to make dua (supplications); the direction to avoid when relieving oneself or spitting; and the direction to which the deceased are aligned when buried. The qibla may be observed facing the Kaaba accurately (ayn al-ka'bah) or facing in the general direction (jihat al-ka'bah). Most Islamic scholars consider that jihat al-ka'bah is acceptable if the more precise ayn al-ka'bah cannot be ascertained. The most common technical definition used by Muslim astronomers for a location is the direction of the great circle—in the Earth's sphere—passing through the location and the Kaaba. This is the direction of the shortest possible path from a place to the Kaaba, and allows the exact calculation (hisab) of the qibla using a spherical trigonometric formula that takes the coordinates of a location and of the Kaaba as inputs (see formula below). The method is applied to develop mobile applications and websites for Muslims, and to compile qibla tables used in instruments such as the qibla compass. The qibla can also be determined at a location by observing the shadow of a vertical rod on the twice-yearly occasions when the sun is directly overhead in Mecca—on 27 and 28 May at 12:18 Saudi Arabia Standard Time (09:18 UTC), and on 15 and 16 July at 12:27 SAST (09:27 UTC). Before the development of astronomy in the Islamic world, Muslims used traditional methods to determine the qibla. These methods included facing the direction that the companions of Muhammad had used when in the same place; using the setting and rising points of celestial objects; using the direction of the wind; or using due south, which was