
Christians believe in one God not many gods. The biblical God is manifest in three persons — the Father, the Son and the Holy Spirit — but all are part of the same Godhead. (All bold are my emphases added. Square brackets [ ] indicate meanings of words. King James Version Easy-Reading Bible (KJVER) used.)
One God

YHWH is mentioned about 7000 times in the bible. God is mentioned about 9000 times and always as one God. Christian’s do not believe in a plural god or polytheism like the Muslim’s claim. He is the Creator.
Deuteronomy 6:4 Hear, O Israel: The LORD [YHWH] our God is one LORD [YHWH]
In the King James Bible, the word written ‘LORD’ (all capitals) is the transliteration of the 4 Hebrew letters (Y.H.W.H.) for God’s name (the unpronounced name of God). Jews are forbidden to pronounce God’s name. It is sometimes pronounced Yahweh or Yahovah (yeh-ho-vaw’ ). The latter was constructed much later from Yahweh and Adonai (Hebrew for Lord). And we commonly hear the form Jehovah, which is written in the English Bible.
Really God’s name is “I AM” or “I AM that I AM” (Exodus 3:14) meaning “the existing One” or self-existent one. This is what God meant when He said “I AM”. The word rendered ‘God’ here is ‘elohiym (pronounced el-o-heem’). Also we find the Hebrew word for God ‘el (pronounced ale)in the Bible. For example, in Psalms 22:1. Its meaning is the ‘Almighty.’
Exodus 3:14 And God said to Moses, I AM THAT I AM: and He said, Thus shall you say to the children of Israel, I AM has sent me to you.
Jesus quoted from Deuteronomy 6:4 when he said,
Mark 12:29 …The first of all the commandments is, Hear, O Israel; The Lord our God is one Lord:
Of course, the New Testament was written mostly in Greek so the Hebrew words are not found there. But the meaning is the same.
Isaiah 35:4 Say to them that are of a fearful heart, Be strong, fear not: behold, your God will come with vengeance, even God with a recompence; He will come and save you.
Isaiah 43:11,12 I, even I, am the LORD; and beside me there is no savior. 12 I have declared, and have saved, and I have showed, when there was no strange god among you: therefore you are My witnesses, saith the LORD, that I am God.
Isaiah 44:6 Thus says the LORD the King of Israel, and his Redeemer the LORD of hosts; I am the First, and I am the Last; and beside me there is no God.
Compare this to:
Revelation 2:8 These things says the First and the Last, which was dead and is alive.
That is Christ, who died and was resurrected the third day. In the book of the Revelation of Jesus Christ he is also identified as:
Revelation 1:8 I am Alpha and Omega, the beginning and the ending, says the Lord, which is, and which was, and which is to come, the Almighty.

Remember the word ‘God’ translated from the Hebrew word ‘el means the Almighty, who was there before the beginning of time because He created time and will be there at the end. The Chinese call the Almighty ‘ShangDi’ or ‘Celestial Emperor,’ which in Chinese means ‘the God above all gods.’
Isaiah 45:5,6 I am the LORD, and there is none else, there is no God beside Me: I girded you, though you have not known Me: 6 That they may know from the rising of the sun, and from the west, that there is none beside Me. I am the LORD, and there is none else.
Isaiah 45:21,22 Tell you, and bring them near; yea, let them take counsel together: who has declared this from ancient time? who has told it from that time? have not I the LORD? and there is no God else beside Me; a just God and a Savior; there is none beside Me. 22 Look to Me, and be you saved, all the ends of the earth: for I am God, and there is none else.
Romans 3:30 Seeing it is one God, which shall justify the circumcision by faith, and uncircumcision through faith.
1 Corinthians 8:6 But to us there is but one God, the Father, of whom are all things, and we in Him; and one Lord Jesus Christ, by whom are all things, and we by Him.
Galatians 3:20 Now a mediator is not a mediator of one, but God is one.
1 Timothy 2:5 For there is one God, and one mediator between God and men, the man Christ Jesus;
James 2:19 You believe that there is one God; you do well: the devils [demons] also believe, and tremble [shudder].
Worship God and Him only
God requires our singular attention. He does not want us running after nor worshipping other gods, especially those of our own making.
Exodus 20:3 You shall have no other gods before Me.
Colossians 2:18 Let no man beguile you of your reward in a voluntary humility and worshipping of angels, intruding into those things which he has not seen, vainly puffed up by his fleshly mind.
Don’t be deceived into worshipping angels, which is nowadays common with the New Age movement. When John, who wrote the book of the Revelation, was taken into a vision of heaven, he beheld an angel,
Revelations 19:10 And I fell at his feet to worship him. And he said to me, See you do it not: I am your fellow-servant, and of your brethren that have the testimony of Jesus: worship God: for the testimony of Jesus is the spirit of prophecy.
Plural Godhead
Genesis 1:26 And God said, Let Us [plural] make man in Our image [singular], after Our likeness [singular]… .
Genesis 3:22 And the LORD God said, Behold, the man is become as one of Us [plural], to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever:
Isaiah 6:8 Also I heard the voice of the Lord, saying, Whom shall I send, and who will go for Us? Then said I, Here am I; send me.
Plural in the Godhead but not multiple gods. The Lord is one God.
“Trinity” revealed in The New Testament
At Jesus’ baptism, the Spirit descended on Jesus in the form of a dove, and the Father’s voice spoke from Heaven—so all three of the members of the Trinity were clearly present (Matthew 3; Mark 1). Jesus commands believers to be baptized “in the name of the Father and of the Son and of the Holy Spirit” (Matthew 28:19).
Romans 8:3,4 For what the law could not do, in that it was weak through the flesh, God sending His own Son in the likeness of sinful flesh, and for sin [a sacrifice for sin], condemned sin in the flesh: 4 That the righteousness [righteous requirement] of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.
God the Father sent God the Son to take away sin, and God the Spirit helps us to live according to the forgiveness granted to us by God the Father, but only after the work of the Son was accepted. Thus, contrary to certain “Oneness” groups, the three Persons are distinct, not merely different modes or manifestations of one Person.
1 Corinthians 12:4-6 Now there are diversities of gifts, but the same Spirit. 5 And there are differences of administrations [ministries], but the same Lord. 6 And there are diversities of operations, but it is the same God which works all in all.
Jude 1:20,21 But you, beloved, building up yourselves on your most holy faith, praying in the Holy Ghost, 21 Keep yourselves in the love of God, looking for the mercy of our Lord Jesus Christ to eternal life.
Holy Spirit is God
When Ananias, with Sapphira his wife, sold a certain possession they lied to the Apostle Peter and to God about it. Scripture reports that Peter said,
Acts 5:3,4 Ananias, why has Satan filled your heart to lie to the Holy Ghost, and keep back part of the price of the land. 4 While it remained, was it not your own? and after it was sold, was it not in your own power? why have you conceived this thing in your heart? you have not lied to men, but to God.
They lied to the Holy Spirit. They lied to God. This clearly shows that the Holy Spirit is God.
Acts 13:2 As they ministered to the Lord, and fasted, the Holy Ghost said, Separate me Barnabas and Saul for the work whereto I have called them.
The Holy Spirit directs God’s work on Earth, and He is everywhere. He is omnipresent.
Psalms 139:7,8 Where shall I go from Your Spirit? or where shall I flee from Your presence? 8 If I ascend up into heaven, You are there: if I make my bed in hell [Hebrew שְׁאוֹל sh’owl (the grave)], behold, You are there.
1 Corinthians 2:10 But God has revealed them to us by His Spirit: for the Spirit searches all things, yea, the deep things of God.
Jesus is God
John 20:28 And Thomas answered and said to him, My Lord and My God.
Jesus is both Lord and God. Thomas, the disciple who expressed his doubts, here recognised Jesus as God.
2 Timothy 1:2 To Timothy, my dearly beloved son: Grace, mercy, and peace, from God the Father and Christ Jesus our Lord.
The Father is God and Jesus our Lord. They are one God.
Titus 2:13 Looking for that blessed hope, and the glorious appearing of the great God and our Savior Jesus Christ;
The Father sends His Son to Earth. Jesus we have established is God.
John 6:29 Jesus answered and said to them, This is the work of God, that you believe on Him whom He has sent.
John 7:29 But I know Him: for I am from Him, and He has sent Me.
John 8:42 Jesus said to them, If God were your Father, you would love Me: for I proceeded forth and came from God; neither came I of Myself, but He sent Me.
The Father sends the Spirit, whom we have established is God.
John 14:26 But the Comforter, which is the Holy Ghost, whom the Father will send in My name [power and authority], He shall teach you all things, and bring all things to your remembrance, whatsoever I have said to you.
Father is God
John 4:21-23 Jesus says to her, Woman, believe Me, the hour comes, when you shall neither in this mountain, nor yet at Jerusalem, worship the Father. 22 You worship you know not what: we know what we worship: for salvation is of the Jews. 23 But the hour comes, and now is, when the true worshippers shall worship the Father in spirit and in truth: for the Father seeks such to worship Him.
John 14:28 You have heard how I said to you, I go away, and come again to you. If you loved Me, you would rejoice, because I said, I go to the Father: for My Father is greater than I.
Philippians 2:5-11 Let this mind be in you, which was also in Christ Jesus: 6 Who, being in the form of God, thought it not robbery to be equal with God: 7 But made Himself of no reputation, and took upon Him the form of a servant, and was made in the likeness of men: 8 And being found in fashion as a man, He humbled Himself, and became obedient to death, even the death of the cross. 9 Wherefore God also has highly exalted Him, and given Him a name [power and authority] which is above every name: 10 That at the name of Jesus every knee should bow, of things in heaven, and things in earth, and things under the earth; 11 And that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father.
John 1:1,14,18 In the beginning was the Word, and the Word was with God, and the Word was God. 14 And the Word was made flesh, and dwelt among us, (and we beheld His glory, the glory as of the only begotten of the Father,) full of grace and truth. 18 No man has seen God at any time; the only begotten Son, which is in the bosom of the Father, He has declared Him.
The Father prepared Christ a body as a flesh human. He descends from heaven to do God’s will.
Hebrews 10:5-7 Wherefore when He comes into the world, He says, Sacrifice and offering You would [desired] not, but a body have You prepared Me: In burnt offerings and sacrifices for sin You have had no pleasure. 7 Then said I, Lo, I come (in the volume of the book it is written of Me,) to do Your will, O God.
Jesus and the Father are the same God.
John 10:30 I and my Father are one.
There is a full measure of divinity in Christ.
Colossians 2:9 For in Him dwells all the fulness of the Godhead bodily.
John 10:28,29 And I give to them eternal life; and they shall never perish, neither shall any man pluck them out of My hand. 29 My Father, which gave them Me, is greater than all; and no man is able to pluck them out of My Father’s hand.
Colossians 1:12-19 Giving thanks to the Father, which has made us meet to be partakers of the inheritance of the saints in light: 13 Who has delivered us from the power of darkness, and has translated us into the kingdom of his dear Son: 14 In whom we have redemption through His blood, even the forgiveness of sins: 15 Who is the image of the invisible God, the firstborn of every creature: 16 For by Him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by Him, and for Him: 17 And He is before all things, and by Him all things consist. 18 And He is the head of the body, the church: who is the beginning, the firstborn from the dead; that in all things He might have the preeminence. 19 For it pleased the Father that in Him should all fulness dwell;
Jesus is Creator.
Hebrews 1:2 Has in these last days spoken to us by His Son, whom He has appointed heir of all things, by whom also He made the worlds [universe];
Jesus Christ is eternal–that is the definition of God.
Hebrews 13:8 Jesus Christ the same yesterday, and to day, and for ever.
Sometimes you hear the claim that God’s son is not mentioned in the Hebrew scriptures, the Old Testament.
Proverbs 30:4 Who has ascended up into heaven, or descended? who has gathered the wind in His fists? who has bound the waters in a garment? who has established all the ends of the earth? what is His name, and what is His son’s name, if you can tell?
Let’s now compare with Islamic teachings
Quran 3:64 Say: “O People of the Book! Come to common terms as between us and you: That we worship none but Allah; that we associate no partners with Him; that we erect not, from among ourselves, lords and patrons other than Allah.”
Allah has no son.
Quran 4:171 O People of the Book! Commit no excesses in your religion: Nor say of Allah aught but the truth. Christ Jesus the son of Mary was no more than an apostle of Allah, and His Word, which He bestowed on Mary, and a Spirit proceeding from Him: So believe in Allah and His apostles. Say not “Trinity:” desist: It will be better for you: For Allah is One God: …: Far Exalted is He above having a son. To Him belong all things in the heavens and on earth.
But remember.
John 1:1-3,14 In the beginning was the Word, and the Word was with God, and the Word was God. 2 The same was in the beginning with God. 3 All things were made by him; and without him was not any thing made that was made. 14 And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
Quran 5:19 In blasphemy indeed are those that say that Allah is Christ the son of Mary. Say “Who then hath the least power against Allah, if His Will were to destroy Christ the son of Mary, his mother, and all–– every one that is on the earth? ….”
2 John 1:7 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.
In the Quran Jesus is called Isa and is the same person as al-Masih (the Messiah) (Quran 2:80-84) Isa’s mother was Maryam, the daughter of Imran (Quran 3:30-34), and sister of Aaron and Moses (Quran 19:29). Which is impossible because Maryam sister of Moses lived 1500 years before Christ was born. According to the Quran Maryam was fostered by Zachariah (the father of John the Baptist) (Quran 3:30-34). It shows how garbled was Muhammad’s understanding of the true history of the Bible.
But the Quran teaches of a Virgin birth (Quran 3:40-44). Maryam was alone in desolate place, under date palm not in Bethlehem (Quran 19:20-25).
Christians are claimed by the Qur’an to believe in a family of gods — Father God, mother Mary and ‘Isa the son — but ‘Isa rejected this teaching. (Al-Ma’idah 5:116)
The doctrine of the Trinity is equated to disbelief and a painful doom awaits those who believe it. (Al-Ma’idah 5:73)
But Scripture warns….
Galatians 1:6-8 I marvel that you are so soon removed from Him that called you into the grace of Christ to another [a different] gospel: 7 Which is not another; but there be some that trouble you, and would pervert [distort] the gospel of Christ. 8 But though we, or an angel from heaven, preach any other gospel to you than that which we have preached to you, let him be accursed [condemned].
In Muhammad’s case he is said to have received his revelations from an angel. But what sort of angel?