Abraham fathered sons by his wife Sarah and her servant Hagar.
Abraham fathered sons by his wife Sarah and her servant Hagar.

Judaism, Christianity and Islam share a common heritage, each having arisen and come to prominence in the Ancient Middle East. Today, Christianity represents 33% of the world's population and Islam represents 21%. Judaism, which has an estimated 14 million adherents (0.22% of the world's population), was foundational to both, particularly in its teachings about monotheism, the concept that there is only one God.

Abraham

Judaism, Christianity and Islam share a common ancestor -- Abraham. Abraham's story is told in the Book of Genesis (chapters 11-25 in the Christian Bible) and in the Quran. All three religions claim to be heir of the faith of Abraham. All three religions also agree that Abraham was born into a family which practiced idolatry, but that he forsook idolatry to pursue the one true God. Estimates vary, but most place Abraham between 1800 BCE and 1600 BCE.

Judaism

According to biblical accounts, Judaism developed while the Israelites were enslaved in Egypt. It was during this time and the time of the exodus, which most scholars place in the 14th century BCE, that Judaism's most sacred text, the Torah, was written. Jewishness is also considered by many as an ethnicity. Jewish people have suffered through eradication attempts during the Nazi Holocaust.

Christianity

Christianity traces its beginning to the life and teachings of Jesus of Nazareth. According to biblical accounts, Jesus -- who was Jewish -- lived during the time of the Roman occupation of Judea. He was born during a time of political unrest, during which many Jewish people were looking for a Messiah -- promised one -- to deliver them from Roman rule.

According to New Testament accounts, Jesus claimed to be the Messiah, but emphasized that his kingdom was not of this world. Christianity's founding is estimated to be around 27 CE to 30 CE, during the time of the Roman Empire.

Christianity grew rapidly during its first three centuries, despite periods of severe persecution from Roman authorities. It was declared the state religion of the Roman Empire towards the end of the 4th century. It then became the dominant religion of Europe and much of Western Asia and Northern Africa. This expansion was achieved by both missionary endeavors and military conquest. During and after the Middle Ages, Christianity split into Orthodox, Catholic, and Protestant divisions.

Islam

Islam began with the preaching of the prophet Muhammad in 610 CE. Muhammad preached that there is only one God - Allah - and that people must live their lives in submission to him.

This message and the religion of Islam spread quickly throughout the Middle East and Mediterranean regions over the following centuries. During the year 622 CE, Muhammad and his followers, having been rejected by the leaders of the city of Mecca, journeyed to Medina, where his message was well received. Many Muslims consider this journey, called the Hijrah, to be the beginning of Islam. Because of this, the Muslim calendar begins in 622 CE.

Islam spread rapidly, both as the result of conquest and interaction of non-Muslims with Muslim merchants along trade routes, becoming the dominant religion of the Arabian Peninsula, North Africa and the Iberian Peninsula by 750 CE. Islam continues to spread through the world and is generally considered the world's fastest growing religion.