"Their scriptures" also say that it is the promised land and God gave it to them. So either you use the Biblical scriptures entirely or you don't, you can't pick and choose parts of the Bible just to confirm your biases.

Anyway, the Hebrew Bible is the largest extant native Levantine literature that remains by far, and it was written by Israelite Jews. If the Palestinians had even 0.0001% of anything close to a volume of native literature like this, they would be parading this around non stop as their proof of indigeneity. It's kind of why the PA wanted to claim the Dead Sea scrolls as one of their own artifacts considering there is no such thing as an actual "Palestinian" before the early 20th century.