It is not an uncommon occurrence that during the dialogues with Christians, a Muslim may hear remarks such as the one mentioned here under:
Remark: Muhammad, the author of the Holy Qur’an, was mistaken into believing that Mary (the mother of Jesus), was the third Person of the Holy Trinity. Muhammad was not aware of the fact that the Holy Ghost is the third Person of the Holy Trinity and not Mary.
To substantiate the above misconception, the person making the remark would probably quote the following verse from the Holy Qur’an:
“And behold! Allah will say: “O Jesus the son of Mary! Didst thou say unto men, ‘Take me and my mother for two gods beside Allah?” He will say: “Glory to Thee! Never could I say what I had no right (to say). Had I said such a thing, Thou wouldst indeed have known it. Thou knowest what is in my heart, though I know not what is in Thine. For Thou knowest in full all that is hidden.” Holy Qur’an 5:116
Upon careful study of the above verse, which was revealed by Allah to Prophet Muhammad (peace be upon him) through Allah’s angel Gabriel, and the scrutiny of the following observations, one discovers that Allah has spoken the Truth.
a) Carved or molten images (Statues) of Jesus Christ and his mother Mary, in various sizes and shapes, are to be found in the Catholic Churches, all around the world.
b) Most of these Sacred Statues are placed in the prominent places of the Prayer Halls of these Christian Churches for venerating and worshipping.
c) One would also notice that the majority of the attending congregates would kneel, worship, venerate and pray before these Holy Images as their reverent rituals. Many devoted believers would place lighted candles in front of these Sacred Statues, before paying their homage.
d) These Catholic congregates who venerate Lord Jesus as their God and Virgin Mary as the "Mother of God", do form the bulk of the Christians community. It has been so since the inception of the Roman Catholic Church. The Protestants, who separated from the Roman Catholics, nearly ten centuries after the advent of Islam, do not have the Statues of Mother Mary in their Churches.
e) These observations clearly indicate that Virgin Mary has been venerated with hyperdulia, along with her son Jesus, by the majority of the Christians, from the early years of the Catholicism.
f) As for the Holy Ghost, the third person of the Holy Trinity, no Christian Church has so far instituted its venerating representation, image or semblance for their Churchgoers.
The obvious conclusion is that for all practical purpose and in reality, when the issue is of Worshipping, Venerating, Deifying and/or Idolizing, it is Mary - the "Mother of God" and not the Holy Ghost has that kind of rank and status. Briefly, the historical figures of Jesus and Mary are venerated as Deities. The Holy Ghost is not venerated as a Deity.
The quoted verse from the Holy Qur’an questions such Divine Ranks and Status that have been assigned by the followers of Jesus to him and his mother. The verse does not speak of the Church developed enigmatic Doctrine of Trinity.
Theologically speaking, the concept of Holy Ghost as ‘Filioque’(“a double procession”) was added to the Original Doctrine much later. As taught by the Greek theologians and advocated by St. Augustine, it simply makes the Holy Ghost a “go-between” communications or things that proceed from the Father and is received by an individual via Jesus Christ. One may argue that since the Holy Ghost emanates from God the Father, it is also God. In reality, this would only be possible if there was a "total emanation" (100% transfer). If that be the case, then the Primary Source has either annihilated Himself (Itself) or has produced a Clone. God the Father still exists and Christians with their Trinitarian Beliefs yet claim God is One.
During his ministry, Jesus Christ had taught in very explicit language to worship the “Father in Heaven” (see Matthew 6:5-13). Jesus never ever taught his followers to make images of him and/or his mother and then venerate either of them. In this regards, the Protestants consider themselves a step ahead and reformed than their counterparts.
The quoted verse from the Holy Qur’an is a direct challenge to those who make the graven images of Jesus and Mother Mary. The Almighty God in the Second of the Ten Commandments also warns mankind against making of graven images and worshipping them. (See Exodus 20:4).