Himself leads a Passover Seder - this is directly from the haggadah to remind Jews of their history of being oppressed in Egypt and to not do the same to others. i doubt he pulled out his Hebrew Scripture for inspiration - but drew upon his experience with Passover.
He did not pull out anything.
This came from one of his speechwriters. I would make the assumption that he has a black speechwriter who is in their late twenties or early thirties.
The speech sounded more like a sermon or rally speech from a black preacher than it did President. And while the youngster would not know the scripture- he is savvy enough to know that all great black speakers throw in a little scripture to make them sound holy.
It just helps to understand context.
The passage referenced alludes to strangers who appear, introduce themselves, and pledge to be productive members of society. It does not refer to hobos walking down the tracks into your backyard because you have pies on the window.