Lynn Cohick explains the why and how of early Christian opposition to exposure.
The Christians struggled against this whole business of exposing children. And from this, they picked up from the Jews. The Jews did not expose their children. They believed that the child was a gift from God, and so to destroy a child’s life was to destroy what God had made.
Later, when Constantine became Emperor, and he made Christianity a legal religion, he changed the law. And what he changed – which is so interesting – he changed the power that the father had over the child. So if you expose an infant, you cannot later go back and reclaim it. So the idea was that that would reduce exposing the children. Because if you did it, you were really and truly giving up the child. It was also an attempt to encourage people, should they find a child that was exposed, to take it and raise it as their own. To give it life, and to raise it, because it is a child of God.