In the study of comparative religion, an Abrahamic religion is any of those religions deriving from a common ancient Semitic tradition and traced by their adherents to Abraham ("Father/Leader of many" Hebrew אַבְרָהָם Arabic ابراهيم), a patriarch whose life is narrated in the Hebrew Bible/Old Testament, and as a prophet in the Qur'an.
This forms a large group of related, largely monotheistic religions, generally held to include Judaism, Christianity, Islam, and the Bahá’í Faith (based upon Islam), and comprises about half of the world's religious adherents.
According to the Jewish tradition, Abraham was the first person to reject idolatry, hence he symbolically appears as the founder of monotheistic religions. In that sense, Abrahamic religion could be simply equated with monotheistic religion, but not all monotheistic religions are Abrahamic. In Islam he is considered as the first monotheist and is often refered to as Ibrahim al-Hanif or Abraham the Monotheist. The term, desert monotheism, is sometimes used for a similar purpose of comparison in historical contexts, but not for modern faiths.
All the Abrahamic religions are derived to some extent from Judaism as practiced in ancient kingdoms of Israel and Judah prior to the Babylonian Exile, at the beginning of the 1st millennium BCE. Many believe that Judaism in Biblical Israel was renovated and reformed to some extent in the 6th century BCE by Ezra and other priests returning to Israel from the exile. Samaritanism separated from Judaism in the next few centuries.
Christianity originated in Judea, at the end of the 1st century, as a radically reformed branch of Judaism; it spread to ancient Greece and Rome, and from there to most of Europe, Asia, the Americas, and many other parts of the world. Over the centuries, Christianity split into many separate churches and denominations. A major split in the 5th century separated various Oriental Churches from the Catholic church centered in Rome . Other major splits were the East-West Schism in the 11th century, separating the Roman Catholic Church from the Eastern Orthodox Churches; and the Protestant Reformation of the 16th century, that gave birth to hundreds of independent Protestant denominations.
The origins of Judaism and the ancestral Abrahamic religion are still obscure. The only source generally agreed by all to be canonical that bears on that question is the Genesis book of the Hebrew Bible, which according to Rabbinic tradition was written by Moses after the Exodus from Egypt, sometime in the 2nd millennium BC. According to Genesis, the principles of Judaism were revealed gradually to a line of patriarchs from Adam to Jacob (also called Israel); however the religion was only established when Moses received the Ten Commandments on Mount Sinai, and with the institution of priesthood and temple services.
Islam originated in the 7th century, in the Arabian cities of Mecca and Medina. Although not a dissident branch of either Judaism or Christianity, it explicitly claimed to be a continuation and replacement for them, and echoed many of their principles. According to the Muslim belief, the Qur'an was the final word of God and its message was that of all the prophets.
"The year that Muhammad fled Mecca for Medina was 622, which marks the beginning of the Muslim calendar.
Stinging from the rejection of his own town and tribe, Muhammad's message quickly become more intolerant and ruthless - particularly as he gained power. Islam's holiest book clearly reflects this contrast, with the later parts of the Qur'an adding violence and earthly defeats at the hands of Muslims to the woes of eternal damnation that the earlier parts of the book promises those who will not believe in Muhammad.
It was at Medina that Islam evolved from the relatively peaceful religion (that had thus far been borrowed from others) to the military force that it became during the last ten years of Muhammad's life, in which infidels were evicted or enslaved, converted upon point of death, and even rounded up and slaughtered.
To fund his quest for control, Muhammad first directed his followers to raid Meccan caravans in the holy months, when the victims would least expect it. This was despite the fact that the Meccans were not bothering him in Medina."
More...