It is good for us to be reminded that it will be the Word of God which judges us in the end.  Revelation describes what will happen on that day:

Revelation 20:11-12 (ESV)
¹¹ Then I saw a great white throne and him who was seated on it. From his presence earth and sky fled away, and no place was found for them.
¹² And I saw the dead, great and small, standing before the throne, and books were opened. Then another book was opened, which is the book of life. And the dead were judged by what was written in the books, according to what they had done.

Notice that “books were opened,” and that “the dead were judged by what was written in the books, according to what they had done.”  What books would those be?

Jesus answers this question:

John 12:47-50 (ESV)
⁴⁷ If anyone hears my words and does not keep them, I do not judge him; for I did not come to judge the world but to save the world.
⁴⁸ The one who rejects me and does not receive my words has a judge; the word that I have spoken will judge him on the last day.
⁴⁹ For I have not spoken on my own authority, but the Father who sent me has himself given me a commandment—what to say and what to speak.
⁵⁰ And I know that his commandment is eternal life. What I say, therefore, I say as the Father has told me.

Notice that Jesus specifically says that “the word that I have spoken will judge him on the last day.”

What words of Jesus would those be?  Would they be just the words which are in red in a lot of Bible translations, the words he spoke which are found in Matthew, Mark, Luke, and John?

Not necessarily.  On the night before he died, Jesus said the following to his apostles:

John 14:25-26 (ESV)
²⁵ These things I have spoken to you while I am still with you.
²⁶ But the Helper, the Holy Spirit, whom the Father will send in my name, he will teach you all things and bring to your remembrance all that I have said to you.

John 16:12-15 (ESV)
¹² “I still have many things to say to you, but you cannot bear them now.
¹³ When the Spirit of truth comes, he will guide you into all the truth, for he will not speak on his own authority, but whatever he hears he will speak, and he will declare to you the things that are to come.
¹⁴ He will glorify me, for he will take what is mine and declare it to you.
¹⁵ All that the Father has is mine; therefore I said that he will take what is mine and declare it to you.

Jesus was basically promising his apostles that after his departure, the Holy Spirit would come and miraculously inspire them, i.e., directly give them teachings which Jesus himself would give the Spirit to give them, teachings which Jesus would get from his Father.  This the Spirit did, as evidenced by the testimony of the apostles Peter and Paul:

2 Peter 1:19-21 (ESV)
¹⁹ And we have something more sure, the prophetic word, to which you will do well to pay attention as to a lamp shining in a dark place, until the day dawns and the morning star rises in your hearts,
²⁰ knowing this first of all, that no prophecy of Scripture comes from someone’s own interpretation.
²¹ For no prophecy was ever produced by the will of man, but men spoke from God as they were carried along by the Holy Spirit.

Ephesians 3:3-5 (ESV)
³ how the mystery was made known to me by revelation, as I have written briefly.
⁴ When you read this, you can perceive my insight into the mystery of Christ,
⁵ which was not made known to the sons of men in other generations as it has now been revealed to his holy apostles and prophets by the Spirit.

1 Corinthians 2:9-13 (NASB)
⁹ but just as it is written, “Things which eye has not seen and ear has not heard , And which have not entered the heart of man , All that God has prepared for those who love Him.”
¹⁰ For to us God revealed them through the Spirit; for the Spirit searches all things, even the depths of God.
¹¹ For who among men knows the thoughts of a man except the spirit of the man which is in him? Even so the thoughts of God no one knows except the Spirit of God.
¹² Now we have received, not the spirit of the world, but the Spirit who is from God, so that we may know the things freely given to us by God,
¹³ which things we also speak, not in words taught by human wisdom, but in those taught by the Spirit, combining spiritual thoughts with spiritual words.

2 Timothy 3:16-17 (ESV)
¹⁶ All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness,
¹⁷ that the man of God may be competent, equipped for every good work.

1 Corinthians 14:36-38 (ESV)
³⁶ Or was it from you that the word of God came? Or are you the only ones it has reached?
³⁷ If anyone thinks that he is a prophet, or spiritual, he should acknowledge that the things I am writing to you are a command of the Lord.
³⁸ If anyone does not recognize this, he is not recognized.

1 Thessalonians 2:13 (ESV)
¹³ And we also thank God constantly for this, that when you received the word of God, which you heard from us, you accepted it not as the word of men but as what it really is, the word of God, which is at work in you believers.

Notice how both Peter and Paul testified that the writers of the New Testament (and the Old) were inspired by God, specifically by the Holy Spirit, and thus one should take their writings as having come from God and the Lord Jesus.

To sum up, whenever you read your New Testaments you are reading the writings of men who were inspired by the Holy Spirit, who received his message from Jesus, who in turn received his message from the Father.  This is why we call Scripture “the Word of God.”

Jesus is God (John 1:1, 14).  His words — the words of the Holy Spirit-inspired authors of the New Testament — will judge us on the last day (John 12:48).  It is therefore the books of the New Testament which will be opened and judge us on that day (Rev. 20:12).

If you are a Christian and you teach those within your church family (and those outside your church family too) things having to do with Christianity, do you love them enough to teach them only what will be the standard by which they are judged on the last day?  Do you love them enough to be sound in your doctrine, your teaching?

Many do not.  Scripture acknowledges this, and warns about them.  It ought to take you probably just a few minutes to read through the following passages.  It would do you well to take the time to do so:

Matthew 7:15-27 (ESV)
¹⁵ “Beware of false prophets, who come to you in sheep’s clothing but inwardly are ravenous wolves.
¹⁶ You will recognize them by their fruits. Are grapes gathered from thornbushes, or figs from thistles?
¹⁷ So, every healthy tree bears good fruit, but the diseased tree bears bad fruit.
¹⁸ A healthy tree cannot bear bad fruit, nor can a diseased tree bear good fruit.
¹⁹ Every tree that does not bear good fruit is cut down and thrown into the fire.
²⁰ Thus you will recognize them by their fruits.
²¹ “Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but the one who does the will of my Father who is in heaven.
²² On that day many will say to me, ‘Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?’
²³ And then will I declare to them, ‘I never knew you; depart from me, you workers of lawlessness.’
²⁴ “Everyone then who hears these words of mine and does them will be like a wise man who built his house on the rock.
²⁵ And the rain fell, and the floods came, and the winds blew and beat on that house, but it did not fall, because it had been founded on the rock.
²⁶ And everyone who hears these words of mine and does not do them will be like a foolish man who built his house on the sand.
²⁷ And the rain fell, and the floods came, and the winds blew and beat against that house, and it fell, and great was the fall of it.”

Acts 20:29-30 (ESV)
²⁹ I know that after my departure fierce wolves will come in among you, not sparing the flock;
³⁰ and from among your own selves will arise men speaking twisted things, to draw away the disciples after them.

Romans 16:17-18 (ESV)
¹⁷ I appeal to you, brothers, to watch out for those who cause divisions and create obstacles contrary to the doctrine that you have been taught; avoid them.
¹⁸ For such persons do not serve our Lord Christ, but their own appetites, and by smooth talk and flattery they deceive the hearts of the naive.

1 Timothy 1:3-7 (ESV)
³ As I urged you when I was going to Macedonia, remain at Ephesus so that you may charge certain persons not to teach any different doctrine,
⁴ nor to devote themselves to myths and endless genealogies, which promote speculations rather than the stewardship from God that is by faith.
⁵ The aim of our charge is love that issues from a pure heart and a good conscience and a sincere faith.
⁶ Certain persons, by swerving from these, have wandered away into vain discussion,
⁷ desiring to be teachers of the law, without understanding either what they are saying or the things about which they make confident assertions.

1 Timothy 4:1-8 (ESV)
¹ Now the Spirit expressly says that in later times some will depart from the faith by devoting themselves to deceitful spirits and teachings of demons,
² through the insincerity of liars whose consciences are seared,
³ who forbid marriage and require abstinence from foods that God created to be received with thanksgiving by those who believe and know the truth.
⁴ For everything created by God is good, and nothing is to be rejected if it is received with thanksgiving,
⁵ for it is made holy by the word of God and prayer.
⁶ If you put these things before the brothers, you will be a good servant of Christ Jesus, being trained in the words of the faith and of the good doctrine that you have followed.
⁷ Have nothing to do with irreverent, silly myths. Rather train yourself for godliness;
⁸ for while bodily training is of some value, godliness is of value in every way, as it holds promise for the present life and also for the life to come.

1 Timothy 6:3-5 (ESV)
³ If anyone teaches a different doctrine and does not agree with the sound words of our Lord Jesus Christ and the teaching that accords with godliness,
⁴ he is puffed up with conceit and understands nothing. He has an unhealthy craving for controversy and for quarrels about words, which produce envy, dissension, slander, evil suspicions,
⁵ and constant friction among people who are depraved in mind and deprived of the truth, imagining that godliness is a means of gain.

2 Timothy 3:1-9 (ESV)
¹ But understand this, that in the last days there will come times of difficulty.
² For people will be lovers of self, lovers of money, proud, arrogant, abusive, disobedient to their parents, ungrateful, unholy,
³ heartless, unappeasable, slanderous, without self-control, brutal, not loving good,
⁴ treacherous, reckless, swollen with conceit, lovers of pleasure rather than lovers of God,
⁵ having the appearance of godliness, but denying its power. Avoid such people.
⁶ For among them are those who creep into households and capture weak women, burdened with sins and led astray by various passions,
⁷ always learning and never able to arrive at a knowledge of the truth.
⁸ Just as Jannes and Jambres opposed Moses, so these men also oppose the truth, men corrupted in mind and disqualified regarding the faith.
⁹ But they will not get very far, for their folly will be plain to all, as was that of those two men.

2 Timothy 4:3-4 (ESV)
³ For the time is coming when people will not endure sound teaching, but having itching ears they will accumulate for themselves teachers to suit their own passions,
⁴ and will turn away from listening to the truth and wander off into myths.

2 Peter 2:1-22 (ESV)
¹ But false prophets also arose among the people, just as there will be false teachers among you, who will secretly bring in destructive heresies, even denying the Master who bought them, bringing upon themselves swift destruction.
² And many will follow their sensuality, and because of them the way of truth will be blasphemed.
³ And in their greed they will exploit you with false words. Their condemnation from long ago is not idle, and their destruction is not asleep.
⁴ For if God did not spare angels when they sinned, but cast them into hell and committed them to chains of gloomy darkness to be kept until the judgment;
⁵ if he did not spare the ancient world, but preserved Noah, a herald of righteousness, with seven others, when he brought a flood upon the world of the ungodly;
⁶ if by turning the cities of Sodom and Gomorrah to ashes he condemned them to extinction, making them an example of what is going to happen to the ungodly;
⁷ and if he rescued righteous Lot, greatly distressed by the sensual conduct of the wicked
⁸ (for as that righteous man lived among them day after day, he was tormenting his righteous soul over their lawless deeds that he saw and heard);
⁹ then the Lord knows how to rescue the godly from trials, and to keep the unrighteous under punishment until the day of judgment,
¹⁰ and especially those who indulge in the lust of defiling passion and despise authority. Bold and willful, they do not tremble as they blaspheme the glorious ones,
¹¹ whereas angels, though greater in might and power, do not pronounce a blasphemous judgment against them before the Lord.
¹² But these, like irrational animals, creatures of instinct, born to be caught and destroyed, blaspheming about matters of which they are ignorant, will also be destroyed in their destruction,
¹³ suffering wrong as the wage for their wrongdoing. They count it pleasure to revel in the daytime. They are blots and blemishes, reveling in their deceptions, while they feast with you.
¹⁴ They have eyes full of adultery, insatiable for sin. They entice unsteady souls. They have hearts trained in greed. Accursed children!
¹⁵ Forsaking the right way, they have gone astray. They have followed the way of Balaam, the son of Beor, who loved gain from wrongdoing,
¹⁶ but was rebuked for his own transgression; a speechless donkey spoke with human voice and restrained the prophet’s madness.
¹⁷ These are waterless springs and mists driven by a storm. For them the gloom of utter darkness has been reserved.
¹⁸ For, speaking loud boasts of folly, they entice by sensual passions of the flesh those who are barely escaping from those who live in error.
¹⁹ They promise them freedom, but they themselves are slaves of corruption. For whatever overcomes a person, to that he is enslaved.
²⁰ For if, after they have escaped the defilements of the world through the knowledge of our Lord and Savior Jesus Christ, they are again entangled in them and overcome, the last state has become worse for them than the first.
²¹ For it would have been better for them never to have known the way of righteousness than after knowing it to turn back from the holy commandment delivered to them.
²² What the true proverb says has happened to them: “The dog returns to its own vomit, and the sow, after washing herself, returns to wallow in the mire.”

It is my sincere goal for myself as a preacher and writer to never have God classify me among any who are described in the above passages.  Christians preachers and teachers, we must love the souls of our brethren enough to give them nothing but the truth in love.  Do we?