It’s an extrapolation from I Corinthians, wherein Paul describes Jesus Christ as the second or last Adam. I’ve always been puzzled by the awkwardness of this, as Eve was Adam’s mate, not his mother.
There’s lots of extrapolation by people who want to find Scripture to support their doctrine but can’t.
“I’ve always been puzzled by the awkwardness of this, as Eve was Adam’s mate, not his mother.”
There’s no awkwardness at all. Types can work out in different ways. Think about it:
Eve drew her flesh from whom? Adam. They were not just of the same flesh because of marriage. They really were of the same flesh (Gen 2:23).
Christ drew His flesh from whom? Mary. The only way for them to be of the same flesh was for Mary to carry Jesus as a child in her womb as a baby.
There’s no awkwardness there. That’s just the only way it could be done to be similar (same flesh) as Adam and Eve.
Once the first human pair was created, the only way a later pair could have one draw flesh from the other was for there to be a mother-child relationship. There is no other way without God creating a human outside of the human race. How would that person be truly part of the human race without a human mother as others had mothers? No, God the Father wanted His Son to be human in every way but sin so He had to have a mother.