Not only is it not in the Bible, such a phrase infers meaning where none exists. Mary was the mother of the child, Jesus, after the flesh. After the Spirit, Jesus is the Son of God, having no earthly father.
As Jesus grew to adulthood, at some point He assumed the duties of a son to His earthly mother, Mary, apparently because Joseph died (as he is never mentioned after Christ reaches maturity). On the cross He conferred His earthly responsibilities toward His mother to His trusted disciple John, and ONLY John. He said, “Woman, behold your son.” He did not say sons. From then on Mary lived in John’s house. She did not live with Peter, nor James, nor Paul. She lived with John who also outlived all of the other disciples, being the youngest of them.
The title of God is most often used in scripture to refer to the Father or to all three persons of the Godhead simulateously. My point is that Mary IS NOT the mother of God the Father, nor is she mother to God the Holy Spirit. Though Jesus is God in the fullest sense, yet He is not the only person of the Godhead. Therefore, it is accurate to describe Mary as the mother of Jesus, but it is inaccurate to describe her as the mother of God.
This is the simplest of logical fallacies which is the fallacy of division. If there is one black swan in a lake and some white swans also, it would be wrong to say the swans in the lake are black.
Further, Christ existed before Mary. And He was her Lord and Savior. This is the same theological dilema which the pharisees could not comprehend about Christ being the son of David and yet David calling Him “Lord”. (See Matthew 22:41-46.)
I accept the confirmed authority of the apostles and the words that came directly from their lips and preserved for us on the pages of scripture. I reject the self-proclaimed apostolic authority that meets none of the criteria for apostleship specified in scripture by the apostles. Christ commends those who test those who say they are apostles and find them to be liars. (See Revelation 2:2.) Paul defends his apostleship and tells us what the qualifications are which include having seen the risen Christ, having been personally instructed by Him, and having confirming miracles. Such apostles universally condemn the use of idols, yet the Catholic church claims unfounded apostolic authority and claims we should ignore this commandment to supposedly honor Mary by making images of her supposed likeness and bowing to it and making offerings to it and directing our prayers toward it, and invoking blasphemous names such as “mother of God” upon it. No holy angel or apostle ever accepted men bowing to them but all outright forbad it (though Satan saught for Christ to bow to and worship him, and wicked Herod received worship from his audience for which he died).
Add not to His Word lest you be found a liar.
That was excellent!
Indeed, when stating that Israel brought forth Christ, it states "of whom as concerning the flesh Christ came. (Rm. 9:5)