Do you believe everything that you hear about the cure for cancer?
What about the rumors of extraterrestrial life?
What about religion?
We need to be mindful of what we hear, more so with God's word, because the first step that one has to take in order to have salvation is hear the word of God.
Romans 10:17 So then faith cometh by hearing, and hearing by the word of God.

Jesus warns us in His sermon on the mountain of the false teachers in the world.
Matthew 7:15 Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves.

These false teachers teach doctrines of men, which makes for vain worship.
Matthew 15:9 But in vain they do worship me, teaching for doctrines the commandments of men.

Those that teach such are accursed.
Galatians 1:8,9 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed. As we said before, so say I now again, If any man preach any other gospel unto you than that ye have received, let him be accursed.

Those that follow such error are in the same position as those who teach it: accursed. Both those that teach error and those that follow error will go to hell if they do not depart from their ways.
Matthew 15:13,14 But he answered and said, Every plant, which my heavenly Father hath not planted, shall be rooted up. Let them alone: they be blind leaders of the blind. And if the blind lead the blind, both shall fall into the ditch.

In order to know truth from error, we need to try(test) the spirits(teachers).
1 John 4:1 Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world.

We do this by observing the fruits that the spirits(teachers) bear.
Matthew 7:16-20 Ye shall know them by their fruits. Do men gather grapes of thorns, or figs of thistles? Even so every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit. A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit. Every tree that bringeth not forth good fruit is hewn down, and cast into the fire. Wherefore by their fruits ye shall know them.

Though, no matter what fruits other may bear, we are still required to study God's word. Studying is a part of hearing, because listening to someone who bears good fruit is not enough.
2 Timothy 2:15 Study to shew thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth.

God's word will make you free.
John 17:17 Sanctify them through thy truth: thy word is truth.
John 8:32 And ye shall know the truth, and the truth shall make you free.

False doctrine will bring damnation.
2 Peter 2:1-3 But there were false prophets also among the people, even as there shall be false teachers among you, who privily shall bring in damnable heresies, even denying the Lord that bought them, and bring upon themselves swift destruction. And many shall follow their pernicious ways; by reason of whom the way of truth shall be evil spoken of. And through covetousness shall they with feigned words make merchandise of you: whose judgment now of a long time lingereth not, and their damnation slumbereth not.

We also must have the right attitude when hearing. We are told to hear(receive) God's word with meekness.
James 1:21 Wherefore lay apart all filthiness and superfluity of naughtiness, and receive with meekness the engrafted word, which is able to save your souls.

Have you heard the true word of God? Do you have the right attitude when hearing it? Be wary, for if you do not hear His word properly, how can you obey His other commandments properly?
Matthew 7:21-23 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.

Carefully examine what you hear and how you hear(receive) it.

Nicholas Stacks