Ishmael was the son of Abraham and Hagar, the Egyptian handmaid of Abraham's legal wife Sarah (an arrangement made when Sarah thought that she couldn't have children), while Isaac was the son of Abraham and Sarah (after it was discovered that Sarah could have children). The Arab people of today are generally the descendants of Ishmael (as they will quite readily tell you), while the Jews (and all of the Israelites of the other tribes, including the so-called "Lost Ten Tribes" - see The Tribes Of Israel) are the descendants of Isaac. All Israelites and most Arabs are the actual physical descendants of Abraham.
To the descendants of Ishmael, God gave the huge territory (about 1,200,000 square miles, much of which includes vast oil fields which the western industrialized world is highly dependent upon) all around the land of Israel, while to the descendants of Isaac, God gave the relatively tiny land of Israel - from Dan to Beersheba, and from The Jordan River to The Mediterranean Sea (approximately 8,000 square miles, only about 1/150th of the area given to the descendants of Ishmael). The God-commanded territory of the Israelites includes all of Samaria, all of Judea, and all of Jerusalem - every last square inch of it.
Arabs were well-known through Bible History:
Fact Finder: Were Arabians present in Jerusalem at the "birthday of the church" Pentecost, making them among the earliest of Christian converts?