What is sin?  How does the Bible define sin?  Let’s take a look.

There are several passages in the Bible that define sin.  The definitions of sin can be divided into three categories: commission, omission, and a lack of faith.

Commission

A sin of commission is doing something we shouldn’t do.  1 John 3:4 defines sin in this way.

1 John 3:4  Whoever commits sin also commits lawlessness, and sin is lawlessness.

The KJV renders it: “sin is the transgression of the law”.  Sin is breaking God’s law.  1 John 5:17 says something very similar:

1 John 5:17  All unrighteousness is sin, …

What is righteousness?

Psa 119:172  My tongue shall speak of Your word, For all Your commandments are righteousness.

God’s commandments are righteousness, so unrighteousness is anything that goes against God’s commandments.  So, “all unrighteousness is sin”, is saying that anything which goes against God’s commandments is sin.

Omission

A sin of omission is not doing something we should do. James 4:17 defines sin this way.

James 4:17  Therefore, to him who knows to do good and does not do it, to him it is sin.

A lack of faith

The Bible also defines sin as “whatever is not from faith”.

Rom 14:23  But he who doubts is condemned if he eats, because he does not eat from faith; for whatever is not from faith is sin.

This deserves some explanation.  The context here is eating meat sacrificed to idols and eating on certain days.  Paul explained that eating meat sacrificed to idols is not specifically a sin.  However, if someone believes that it is and then proceeds to eat meat sacrificed to idols, he sins.  If you do something which you think is wrong, even though it isn’t, then you sin.  You are not acting according to your belief, which in Biblical terms is “not from faith”.

Belief in God is a righteous action.

Rom 4:3  For what does the Scripture say? “ABRAHAM BELIEVED GOD, AND IT WAS ACCOUNTED TO HIM FOR RIGHTEOUSNESS.”

Thus, disbelief is unrighteousness.  Expressed differently, a lack of faith is sin.  Unbelief in God (turning away from God) is described as evil.

Heb 3:12  Beware, brethren, lest there be in any of you an evil heart of unbelief in departing from the living God;

Summary

We could summarise the different ways of sinning by saying that sin is not showing love.  The two greatest commandments are to love God with all your being, and to love others as yourself.

Mat 22:36  “Teacher, which is the great commandment in the law?”
Mat 22:37  Jesus said to him, ‘YOU SHALL LOVE THE LORD YOUR GOD WITH ALL YOUR HEART, WITH ALL YOUR SOUL, AND WITH ALL YOUR MIND.’
Mat 22:38  This is the first and great commandment.
Mat 22:39  And the second is like it: ‘YOU SHALL LOVE YOUR NEIGHBOR AS YOURSELF.’

Indeed, love is the fulfillment of the law.

Rom 13:10  Love does no harm to a neighbor; therefore love is the fulfillment of the law.

Breaking these two great commandments is sin.  (Sin is transgression of the law, 1 John 3:4.)  In other words, not loving God or not loving others is sin.  Sin is a lack of love.