"I think it goes back to Abraham c 3000bce doesn't it?"
Yup. You got that right.
When God began working with Abram (his name was later changed to Abraham), God gave him a command and an amazing promise. The command was, “Get out of your country, from your family and from your father’s house, to a land that I will show you” (Genesis 12:1).
Explaining the promise He would give Abraham in exchange for his obedience, God continued: “I will make you a great nation; I will bless you and make your name great; and you shall be a blessing. I will bless those who bless you, and I will curse him who curses you; and in you all the families of the earth shall be blessed” (verses 2-3).
Now it seems that Sarah, Abraham's wife, was infertile and no child was forthcoming, so Sarah thought she'd help thing along a bit. She suggested that Abraham have a 'liason' with her (Sarah's) maidservant called Hagar who was an Egyptian slave.
This happened and Hagar has a son called Ishmael.
Everything was tickety-boo until Sarah herself got pregnant and had a son called Isaac.
At this point Hagar was banished with the child under God's instructions to Abraham.
The story can be read in Genesis 21 v 9-21
However God said "As for the son of the slave-woman, I will make a nation of him, too, for he is your seed.”
Now, everything went quiet until Islam was created in the 7th century.
Ishmael is recognized by Muslims as the ancestor of several northern prominent Arab tribes and the forefather of Adnan, the ancestor of Muhammad.
The Hashimites (Jordanian Arabs) claim descent from Ishmael.
So if you are still with me so far, you can see why both Arabs and Jews have a religious claim to the land in question....