Islam and the Bible
Question: What does the Bible say about Islam? Why did God promise great nations to BOTH of Abraham's sons?
Answer: Part of your confusion regarding Islam is probably a result of how you define "nation." It is true that God promised great nations to both Isaac and Ishmael, but what is a "nation"? In all but five instances in the Old Testament where the word "nation" is used, it is the Hebrew word goy, Strong's Concordance #1471, and means a Gentile or heathen nation or people.
Genesis 17 predicts two great nations coming from Abraham and Sarah in their old age. The first great nation sprang from Issac, the only child born to Abraham and Sarah. The second nation would come from Ishmael, Abraham's first child through Hagar (Sarah's servant). It is through Abraham and Ishmael that Islam not only traces its roots but also considers itself an Abrahamic religion.
The twenty-fifth chapter of Genesis names the twelve princes of Ishmael and specifies where they lived. They were, in alphabetical order, Adbeel, Dumah, Hadar, Jetur, Kedar, Kedemah Massa, Mibsam, Mishma, Naphish, Nebajoth, and Tema. God's word states that they lived in Havilah as far as Shur, which is east of Egypt (see Genesis 25:12 - 18). One Scriptural dictionary had the following to say about Ishmael.
Most of the Arab Bedouins recognize Muhammad (571 to 632 A.D.), who originated Islam, as their spiritual leader. This is why there is no mention of it in Holy Writ. Most references refer to them as Moslems, Mohammedans, or Muslims. Genesis 25:20 - 24 tells us that after Isaac and Rebekah married she conceived two children who would represent two nations. The older of the two children would ultimately serve the younger child.