If you knew Christians do not say Gabriel is Holy Spirit, why the claim in the first place? When you say Qur’an explains that Holy Spirit is Angel Gabriel, could you please point me to where it was explained?
As for your question, as I understand it, the concept of Holy Spirit had been there from the beginning (OT), just lacked the term “Holy Spirit” as we understand it now. The same thing with the concept of Trinity had been understood by early Christians (NT), just lacked the term “Trinity”. I’m going to refer to the following for some samples of Holy Spirit in OT and NT:
forums.catholic-questions.org/showpost.php?p=9747063&postcount=10
What’s wrong with God being with us in the world from the beginning? I expect my king, president, prime minister, general, employer, etc to come down to the people/subjects/employees to understand the situations/conditions on the ground in order to better teach and lead the people to a better future, not just giving commands from the throne. If I expect that from human leaders, why can’t I expect God (the King of Kings, no less) to do the same: be with us and teach us, not just exists outside time and space? Or did you just mean God is not bound by time and space by saying “outside time and space”?
87- To Musa (Moses) We gave the Book (Torah) and sent after him other Rasools in succession; then We gave Isa (Jesus), the son of Maryam (Mary), clear Signs and strengthened him with the Holy Spirit (Gabriel). Why is it that whenever there came to you a Rasool with a message which did not suit your desires, you became so arrogant that some you called impostors and others you killed! Al-Baqarah(2)
253- Those messengers We endowed with gifts, some above others: To one of them Allah spoke; others He raised to degrees (of honour); to Jesus the son of Mary We gave clear (Signs), and strengthened him with the holy spirit. If Allah had so willed, succeeding generations would not have fought among each other, after clear (Signs) had come to them, but they (chose) to wrangle, some believing and others rejecting. If Allah had so willed, they would not have fought each other; but Allah Fulfilleth His plan. Al-Baqarah(2)
110- Then Allah will ask: "O Isa (Jesus) son of Maryam (Mary)! Recall my favor upon you and to your mother, how I strengthened you with the Holy Spirit, so you could speak to the people in cradle and in old age, how I taught you the Book, Wisdom, the Taurat (Torah) and the Injeel (Gospel). How you were able to make the figure of a bird out of a clay, by My permission, how you breathed into it and changed it into a real bird, by My permission. How you could heal the born-blind and the lepers by My permission. How you could bring the dead body back to life by My permission. How I protected you from the violence of the Children of Israel when you came to them with clear signs and the unbelievers among them said: “This is nothing but a clear sorcery.” Al-Maidah(5)
102- Say, “The Holy Spirit (Gabriel) has brought it down piecemeal intact from your Rabb to strengthen the faith of the believers, and to give guidance and good news to the Muslims.” An-Nahl(16)
There are also hadiths and interpretations of scholars about Ruh-ul Kudus(Holy Spirit).
If you look at verse which refer to Holy Spirit so you will see that attributions of Holy Spirit could belong to an angel. There is no need to make a human and an angel to be God!
God can see, hear, feel etc very well and lackless without being incarnated? Can God not do that? If God cannot see and feel what I do so God cannot be my God. Yet God create my feels and acts after my choises.
Prophets were sent in name of God and if prophets were angels so they would not be perfect role model for human because people would say that we cannot perform what angels do. God had never sent an angel to preach. Yet God did not sent angels why need to come Himself? Is there any importance either Jesus was God or not? No. Because Jesus lived just as a human and He was a perfect model. If I like Jesus so God will love me. I love Jesus for sake of God.
Insist on claim Jesus to be God make Christianity less reliable.
Jesus could not be so successful perfectly if we think He was God. Many people did not believe in Him and many people did evil things about Him. Why a god be so desperate? God suffered all these for salvation of humanbeing? It seems god! could not do that absolutely many people went/go on wrong ways. And also it seems sacrifice of God as Himself is not enough! Could not God do that without suffering of Himself? God can do.
Think a god who to forgive human is bound on harming Himself! Indeed God do not get harm in any case.
God is out of time and space because God is not bound on time and space. God create time and space and God is not one part of His creatures. Materials are exposed to corruption in time and space. God never corrupt. God knows every thing timeless. Jesus grow gradually. Jesus need food and water and air etc. Does God need anything?
If you say Jesus’s body and essence were different? I ask How? Did Jesus have a humanian soul? If it was in that way so what make Jesus to be God? Or do you say God interacted with soul of Jesus? I ask in which way? And also God may interact with souls by very different ways so are all people God? Can any one explain that?