Abraham and his descendants
Abraham, as told about in the book of Genesis was a Godly and righteous man. God made a covenant with Abraham and promised this covenant to him and his descendants. Abraham did not have any sons at that time so God promised him a son to be his heir. But Abraham's wife, Sarah who was very old didn't believe that could happen, in fact she laughed when two angels of God came and told them that God would give them a son. So because Sarah felt she could not bare a child, she made arraignments for Abraham to have a child with Sarah's servant girl Hagar (the bible refers to her as the bondwoman). Abraham had a Son from Hagar and his name was Ishmael. They showed a lack of faith in God's promise to give them a son. Finally God delivered his promise and Sarah, Abraham's wife bore him a Son who they named Isaac. Because they did not believe in Gods promise, and even though Ishmael was a descendant of Abraham, he, Ishmael, was not the descendant God planned to be the righteous heir of Abraham to the land of Israel.
As the story unfolds, there was conflict between Isaac and Ishmael. Abraham's wife, eventually convinced her husband to have Ishmael and his mother sent away. An angel of God told Hagar, that He would make Ishmael a 'great nation', but he would be;
“...a wild man, His hand shall be against every man and every mans' hand against him”. GEN 16:12.
Some people think that this verse tells us that Ishmael was a person who would become evil and that is how a lot of the problems in the Middle East started. Some Muslims believe that Ishmael was the chosen one that Abraham brought to sacrifice, and that they are entitled to the land of Israel, not the Jewish people, who are the descendants of Isaac. However it is clear from scripture that God's covenant was with Abraham and this covenant would pass to his son Isaac and then to his son Jacob. Ishmael was not included in this covenant.
God spoke about His covenant with Abraham telling him He would bless Abraham and his descendants and that they would be of a number more than he could count. In Genesis chapter 15 explains this covenant from God to Abraham.
...Then He brought him outside and said, “look toward heaven, and count the stars if your able to number them”. And He said to him, So shall your descendants be”. Gen. 15:5
As stated above, this covenant for the land of Israel did not include the descendants of Ishmael. Scripture in the old Testament says as quoted above that the descendants of Ishmael would be of a separate nation.