Bible Verses About Servants: By birth

When Abram heard that his relative was taken captive, he led out his trained men, born in his house, three hundred and eighteen, and pursued as far as Dan.

LORD, truly I am your servant. I am your servant, the son of your handmaid. You have freed me from my chains.

Is Israel a servant? Is he a native-born slave? Why has he become a captive?