'Child' in the Bible

However, you are not [living] in the flesh [controlled by the sinful nature] but in the Spirit, if in fact the Spirit of God lives in you [directing and guiding you]. But if anyone does not have the Spirit of Christ, he does not belong to Him [and is not a child of God].

And not only so, but Rebecca being about to have a child by our father Isaac--

according to his calling and not by actions), Rebecca was told, "The older child will serve the younger one."