But just as then the one born in the manner of flesh began persecuting the one born in the manner of spirit, so also now.

Yes, Isaac’s birth to Abraham was miraculous, absolutely not “in the manner of flesh.” (Genesis 18:11-15) So it had to be “in the manner of spirit.” Yes, the spirit of the Greater Abraham, Jehovah God, surely was needed to revive the reproductive powers of the free woman Sarah, as well as those of Abraham. (Romans 4:19)