Isaiah 43:10 
“You are My witnesses,” declares the Lord, 
"And My servant whom I have chosen,
In order that you may know and believe Me,
And understand that I am He.
Before Me there was no God formed,
And there will be none after Me.

Isaiah 44:8
‘Do not tremble and do not be afraid;
Have I not long since announced it to you and declared it?
And you are My witnesses.
Is there any God besides Me,
Or is there any other Rock?
I know of none.’”

Genesis 3:1-5
1 Now the serpent was more crafty than any beast of the field which the Lord God had made. And he said to the woman, “Indeed, has God said, ‘You shall not eat from any tree of the garden’?” 2 And the woman said to the serpent, “From the fruit of the trees of the garden we may eat; 3 but from the fruit of the tree which is in the middle of the garden, God has said, ‘You shall not eat from it or touch it, lest you die.’” 4 And the serpent said to the woman, “You surely shall not die! 5 “For God knows that in the day you eat from it your eyes will be opened, and you will be like God, knowing good and evil.”

Matthew 24:23-27
23 “Then if anyone says to you, ‘Behold, here is the Christ,’ or ‘There He is,’ do not believe him. 24 “For false Christs and false prophets will arise and will show great signs and wonders, so as to mislead, if possible, even the elect. 25 “Behold, I have told you in advance. 26 “If therefore they say to you, ‘Behold, He is in the wilderness,’ do not go forth, or, ‘Behold, He is in the inner rooms,’ do not believe them. 27 “For just as the lightning comes from the east, and flashes even to the west, so shall the coming of the Son of Man be.

Luke 13:34-35
34 “O Jerusalem, Jerusalem, the city that kills the prophets and stones those sent to her! How often I wanted to gather your children together, just as a hen gathers her brood under her wings, and you would not have it! 35 “Behold, your house is left to you desolate; and I say to you, you shall not see Me until the time comes when you say, ‘Blessed is He who comes in the name of the Lord!’”

Exodus 33:20
But He said, “You cannot see My face, for no man can see Me and live!” 21 Then the Lord said, “Behold, there is a place by Me, and you shall stand there on the rock;

Matthew 22:30
“For in the resurrection they neither marry, nor are given in marriage, but are like angels in heaven.

1Kings 8:27
"Behold, heaven and the highest heaven cannot contain Thee..."

Isaiah 66:1
Thus says the Lord,
“Heaven is My throne, and the earth is My footstool.

Psalm 11:4
...the Lord’s throne is in heaven...

2Corinthians 11:3-4
3 But I am afraid, lest as the serpent deceived Eve by his craftiness, your minds should be led astray from the simplicity and purity of devotion to Christ. 4 For if one comes and preaches another Jesus whom we have not preached, or you receive a different spirit which you have not received, or a different gospel which you have not accepted, you bear this beautifully.

Galatians 1:8-9
8 But even though we, or an angel from heaven, should preach to you a gospel contrary to that which we have preached to you, let him be accursed. 9 As we have said before, so I say again now, if any man is preaching to you a gospel contrary to that which you received, let him be accursed.

1Timothy 4:1
 But the Spirit explicitly says that in later times some will fall away from the faith, paying attention to deceitful spirits and doctrines of demons...

Titus 1:9
...holding fast the faithful word which is in accordance with the teaching, that he may be able both to exhort in sound doctrine and to refute those who contradict.

This teaching is contradicted and shown to be useless by a passage within the book of Mormon itself.  The passage is quoted below:

Alma 34:34-35
34 "Ye cannot say, when ye are brought to that awful crisis, that I will repent, that I will return to my God.  Nay, ye cannot say this; for that same spirit which doth possess your bodies at the time that ye go out of this life, that same spirit will have power to possess your body in that eternal world.  35 For behold, if ye have procrastinated the day of your repentance even until death, behold, ye have become subjected to the spirit of the devil, and he doth seal you his; therefore, the Spirit of the Lord hath withdrawn from you, and hath no place in you, and the devil hath all power over you; and this is the final state of the wicked."

Hebrews 9:27
And inasmuch as it is appointed for men to die once and after this comes judgment...

Mormonism is a polytheistic religion. Joseph Smith declared, "I will preach on the plurality of Gods. I have always declared God to be a distinct personage, Jesus Christ a separate and distinct personage from God the Father, and the Holy Ghost was a distinct personage and a Spirit: and these three constitute three distinct personages and three Gods" (Teachings of the Prophet Joseph Smith, p. 370--quoted from the Watchman Fellowship's web site at http://www.watchman.org/ldspro.htm).

Below are passages in the Book of Mormon that contradict the Mormon doctrine of a Trinity of three distinct gods:

Mosiah 15:3-4
3 The Father, because he was conceived by the power of God; and the Son, because of the flesh; thus becoming the Father and Son-- 4 And they are one God, yea, the very Eternal Father of heaven and of earth.

Alma 11:38-39
38 Now Zeezrom saith again unto him: Is the Son of God the very Eternal Father? 39 And Amulek said unto him: Yea, he is the very Eternal Father of heaven and of earth, and all things which in them are; he is the beginning and the end, the first and the last...

Alma 11:44
Now, this restoration shall come to all, both old and young, both bond and free, both male and female, both the wicked and the righteous; and even there shall not so much as a hair of their heads be lost; but every thing shall be restored to its perfect frame, as it is now, or in the body, and shall be brought and be arraigned before the bar of Christ the Son, and God the Father, and the Holy Spirit, which is one Eternal God, to be judged according to their works, whether they be good or whether they be evil.

3Nephi 11:27
And after this manner shall ye baptize in my name; for behold, verily I say unto you, that the Father, and the Son, and the Holy Ghost are one; and I am in the Father, and the Father in me, and the Father and I are one.

Revelation 22:13 (note: Jesus is speaking; this verse is important to note when reading Isaiah 48:12, quoted right below this passage)
“I am the Alpha and the Omega, the first and the last, the beginning and the end.”

Isaiah 48:12-16 (note: Jesus is speaking as the voice of God through the prophet Isaiah, over 700 years before Jesus' appearance on earth)
12 “Listen to Me, O Jacob, even Israel whom I called;
I am He, I am the first, I am also the last.
13 “Surely My hand founded the earth,
And My right hand spread out the heavens;
When I call to them, they stand together.
14 “Assemble, all of you, and listen!
Who among them has declared these things?
The Lord loves him; he shall carry out His good pleasure on Babylon,
And His arm shall be against the Chaldeans.
15 “I, even I, have spoken; indeed I have called him,
I have brought him, and He will make his ways successful.
16 “Come near to Me, listen to this:
From the first I have not spoken in secret,
From the time it took place, I was there.
And now the Lord God  has sent Me, and His Spirit.”

Psalm 45:7 (God and the Messiah [the Anointed One] are both God)
Thou hast loved righteousness, and hated wickedness;
Therefore God, Thy God, has anointed Thee
With the oil of joy above Thy fellows.

Titus 2:13 (Jesus is God)
 ...looking for the blessed hope and the appearing of the glory of our great God and Savior, Christ Jesus.

John 20:28-29 (Jesus is God)
28 Thomas answered and said to Him, “My Lord and my God!” 29 Jesus said to him, “Because you have seen Me, have you believed? Blessed are they who did not see, and yet believed.”

The sixth LDS prophet, Joseph F. Smith explains that the Holy Spirit is not a person but rather an impersonal force. "You may call it the Spirit of God, you may call it the influence of God's intelligence, you may call it the substance of his power; no matter what it is called, it is the spirit of intelligence that permeates the universe" (Mormon Doctrine, McConkie, pp. 752-753--quoted from the Watchman Fellowship's web site at http://www.watchman.org/ldspro.htm).

John 16:13-14
13 “But when He, the Spirit of truth, comes, He will guide you into all the truth; for He will not speak on His own initiative, but whatever He hears, He will speak; and He will disclose to you what is to come. 14 “He shall glorify Me; for He shall take of Mine, and shall disclose it to you.

Below are passages in the Book of Mormon:

2Nephi 25:23
For we labor diligently to write, to persuade our children, and also our brethren, to believe in Christ, and to be reconciled to God; for we know that it is by grace that we are saved, after all we can do.

Mosiah 5:15
Therefore, I would that ye should be steadfast and immovable, always abounding in good works, that Christ, the Lord God Omnipotent, may seal you his, that you may be brought to heaven, that ye may have everlasting salvation and eternal life, through the wisdom, and power, and justice, and mercy of him who created all things, in heaven and in earth, who is God above all. Amen.

Mosiah 13:28
And moreover, I say unto you, that salvation doth not come by the law alone; and were it not for the atonement, which God himself shall make for the sins and iniquities of his people, that they must unavoidably perish, notwithstanding the law of Moses.

3Nephi 11:37-38
37 And again I say unto you, ye must repent, and become as a little child, and be baptized in my name, or ye can in nowise receive these things. 38 And again I say unto you, ye must repent, and be baptized in my name, and become as a little child, or ye can in nowise inherit the kingdom of God.

Ephesians 2:8-9
8 For by grace you have been saved through faith; and that not of yourselves, it is the gift of God; 9 not as a result of works, that no one should boast.

Galatians 2:16
...nevertheless knowing that a man is not justified by the works of the Law but through faith in Christ Jesus, even we have believed in Christ Jesus, that we may be justified by faith in Christ, and not by the works of the Law; since by the works of the Law shall no flesh be justified.

Luke 23:39-43
39 And one of the criminals who were hanged there was hurling abuse at Him, saying, “Are You not the Christ? Save Yourself and us!” 40 But the other answered, and rebuking him said, “Do you not even fear God, since you are under the same sentence of condemnation? 41 “And we indeed justly, for we are receiving what we deserve for our deeds; but this man has done nothing wrong.” 42 And he was saying, “Jesus, remember me when You come in Your kingdom!” 43 And He said to him, “Truly I say to you, today you shall be with Me in Paradise.”

John 3:14-16
14 “And as Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up; 15 that whoever believes may in Him have eternal life.
16 “For God so loved the world, that He gave His only begotten Son, that whoever believes in Him should not perish, but have eternal life.

Psalm 90:2
Before the mountains were born,
Or Thou didst give birth to the earth and the world,
Even from everlasting to everlasting, Thou art God.

Psalm 93:2
Thy throne is established from of old;
Thou art from everlasting.

Habakkuk 1:12
Art Thou not from everlasting,
O Lord, my God, my Holy One?

Matthew 24:35
"Heaven and earth will pass away, but My words shall not pass away."

Isaiah 8:20
To the law and to the testimony! If they do not speak according to this word, it is because they have no dawn.

Isaiah 40:8
The grass withers, the flower fades,
But the word of our God stands forever.