The belief that Mary was the Mother of God by means of bearing in her womb the Savior’s body was already a universal belief. I say
universal since not only the Catholics, but even the Protestants uphold this Marian doctrine. Protestants, in clinging to the explanation that since Jesus is God and Mary conceived Him, therefore Mary should be regarded as the Mother of God. From this simple explanation, all the doctrines relating to the veneration of Mary arise among the Christendom, so its not surprising if Protestant denominations will soon venerate Mary in the way the Catholic does.
For a great period of time, the claim about the motherhood of Mary to God was defended by the Catholic Church, though in reality, the Bible never mentioned anything about this subject. The belief about Theotokos lies upon the weak understanding of Christ’s dual nature. The dual nature of Christ – the divine and human – are well explained by the Holy Scriptures, yet it is a very sensitive subject that a little wrong understanding may contribute to the rise of a false doctrine.
In his letter, Apostle John stated;
“For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist.” (II John 1:7)
The anti-Christ will tell us that Christ didn’t come in the flesh, but what if a preacher will tell us that Christ is the VERY FLESH which was conceived by Mary? Well, that’s unbiblical and unchristian, too. The Spirit of Christ, which is the begotten Son of God, is different from the flesh which Mary conceived. It was understood that the flesh which was conceived by Mary during her virginity is the body of Christ, the vessel which the Spirit of Christ used in order to fulfill the work of salvation planned by the Father. Except Christ will partake with the nature of man, He will never fulfill the work of redemption through death. The Holy Scripture stated;
Forasmuch then as the children are partakers of flesh and blood, he also himself likewise took part of the same; that through death he might destroy him that had the power of death, that is, the devil; (Hebrews 2:14)
And again the Spirit of Christ Himself declared;
Wherefore when he cometh into the world, he saith, Sacrifice and offering thou wouldest not, but a body hast thou prepared me: (Heb. 10:5)
Apostle Paul gave us a clear view about the meaning of the “flesh” when he said;
For we that are in this tabernacle do groan, being burdened: not for that we would be unclothed, but clothed upon, that mortality might be swallowed up of life. (II Corinthians 5:4)
Our body is a tabernacle, the dwelling place of a righteous spirit; the same as the body of Christ where the Spirit of the Son dwelt in. By means of the body of flesh and blood, the Son suffered the consequences of sin, experienced the emotional and the physical weaknesses of man, and fulfilled the sacrificial offering at the cross. After the sacrificial offering at the Calvary, the body of Christ was changed into a glorified body; a body that can survive in eternity. Paul said;
Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption. (I Corinthians 15:50)
The body of Christ before the crucifixion was changed. And concerning to this transformation, the apostle said, “Wherefore henceforth know we no man after the flesh: yea, though we have known Christ after the flesh, yet now henceforth know we him no more.” (II Corinthians 5:16). The present heavenly body of Christ is not the same as before the crucifixion. It is not the same as what Mary conceived. The role of Mary was already passed and we cannot still say that she is the Mother of Christ, neither the Mother of God.
Marwil Llasos, an apologist and a blogger defending the Catholic faith clarified that;
Source: Mary: The Mother of God by Marwil N. Llasos
The flesh was already sacrificed and Christ reinstated to His original nature – the nature which Mary never conceived but begotten by God in eternity.