I am pasting in one of my previous posts about this.
The quran states quite clearly that God is one, and it is a blasphemy to say Jesus is the son of God, at sura 5.72 and it is a blasphemy to say God is part of a trinity. at sura 5.73.
Sura 5.72 They do blaspheme who say: "Allah is Christ the son of Mary"
Sura 5.73 They do blaspheme who say: Allah is one of three in a Trinity: for there is no God except One God.
But the bible says you may be forgiven for blasphemy against Jesus, but to deny the Holy Ghost will not be forgiven. Therefore if the bible is right then Muhammad was an unforgivable blasphemer.
Only one book can be right, and there is no room for adjustment here. So it is quite clear that the quran does not confirm all the previous messages, as it claims to do at sura 10.37
Sura 10.37 This quran is not such as can be produced by other than Allah; on the contrary it is a confirmation of revelations that went before it, and a fuller explanation.
It is clear where Muhammad got the idea of claiming he received the quran from the angel Gabriel in the bible, as the angel is sent to Zacharias to tell him of the coming of John the baptist at Luke 1.11 to 1.20 The angel Gabriel also visited Mary to tell her about Jesus at Luke 1.27
But the bible states that it was the Holy Ghost that spoke through Jesus, and later the through the disciples, so the angel Gabriel was not required to tell the word of God, as God himself in the form of the holy Ghost speaks with the mouth of his true messengers.
Therefore what doubt can there be that Muhammad invented a lie about God, and said he was told what was written on a tablet in heaven, and he remembered the message and passed it on to his followers. There can be no clearer indictment of Muhammad as a false prophet than the denial of the trinity, and the power of the holy spirit to speak through a true messenger.
Muhammad could not speak without thinking about his words, as he might contradict himself or make errors. Which of course, he did do anyway. But he gave himself time to go away and think up his next statement by claiming he had to get the message from Gabriel.
The following are the bible texts that state denying the Holy Ghost is an unforgivable sin, but denying Jesus is not.
Matthew:12:31: Wherefore I say unto you, All manner of sin and blasphemy shall be forgiven unto men: but the blasphemy against the Holy Ghost shall not be forgiven unto men.
Matthew:12:32: And whosoever speaketh a word against the Son of man, it shall be forgiven him: but whosoever speaketh against the Holy Ghost, it shall not be forgiven him, neither in this world, neither in the world to come.
Matthew

29: But he that shall blaspheme against the Holy Ghost hath never forgiveness, but is in danger of eternal damnation:
Luke:12

And whosoever shall speak a word against the Son of man, it shall be forgiven him: but unto him that blasphemeth against the Holy Ghost it shall not be forgiven.
These are some more verses that explain the concept that the Holy Ghost is God within us. which is the message Muhammad denies, and for which there is no forgiveness.
1Co:6

What? know ye not that your body is the temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own?
1Co:12

Wherefore I give you to understand, that no man speaking by the Spirit of God calleth Jesus accursed: and that no man can say that Jesus is the Lord, but by the Holy Ghost.
1Jo:5:7: For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one.
The only conclusion anyone can really draw from this complete contradiction between the message of the New Testament, that the Holy Ghost enters true prophets, and God speaks through them, and the message of the quran that Muhammad claims he received as dictation from the angel Gabriel.
Is that Muhammad has committed the unforgivable blasphemy by denying The holy ghost and that Jesus was a part of God, and as a consequence denying the concept that God is within us all. So by the terms of the New Testament, Muhammad has and consigned himself to hell.