The Bible views the heart in a much different way than we typically do. The first mention of the heart is in Genesis 6:5 where it says, “The LORD saw that the wickedness of man was great in the earth, and that every intention of the thoughts of his heart was only evil continually.” What we think in our minds is important with regard to spiritual activity. If all we ever think about is evil, we will not be able to do what God wants us to. Jesus told his disciples, “Do you not see that whatever goes into the mouth passes into the stomach and is expelled? But what comes out of the mouth proceeds from the heart, and this defiles a person. For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false witness, slander. These are what defile a person” (Matthew 15:18-20).

Moses instructed the people of Israel to “love the LORD your God with all your heart” (Deuteronomy 6:5). The Hebrew word that is translated heart, lebab (lay-bawbˊ) is “a masculine noun meaning heart, mind, inner person. The primary usage of this word describes the entire disposition of the inner person that God can discern…It is also used to describe the place where the rational, thinking process occurs that allows a person to know God’s blessing (Joshua 23:14); to plan for the future (1 Kings 8:18); to communicate (2 Chronicles 9:1); and to understand God’s message (Isaiah 6:10). Like the English usage, it often refers to the seat of the emotions, whether it refers to joy (Deuteronomy 28:47); discouragement (Joshua 2:11); comfort (Judges 19:8); grief (1 Samuel 1:8); sorrow (Psalm 13:2[3]); or gladness (Isaiah 30:29)” (H3824).

Deuteronomy 10:16 talks about circumcising the foreskin of your heart. Circumcision was what distinguished the Israelites from all other people. When God established his covenant with Abraham, he said, “This is my covenant, which you shall keep, between me and you and your offspring after you: Every male among you shall be circumcised. You shall be circumcised in the flesh of your foreskins, and it shall be a sign of the covenant between me and you” (Genesis 17:10-12). Moses later told the people of Israel, “And the LORD your God will circumcise your heart and the heart of your offspring, so that you will love the LORD your God with all your heart and with all your soul, that you may live” (Deuteronomy 30:6).

Jesus used the illustration of a tree bearing fruit to explain the connection between our hearts and what comes out of our mouths. Speaking to the Pharisees, religious leaders who were known for their religious hypocrisy, Jesus said:

“Either make the tree good and its fruit good, or make the tree bad and its fruit bad, for the tree is known by its fruit. You brood of vipers! How can you speak good, when you are evil? For out of the abundance of the heart the mouth speaks. The good person out of his good treasure brings forth good, and the evil person out of his evil treasure brings forth evil. I tell you, on the day of judgment people will give account for every careless word they speak, for by your words you will be justified, and by your words you will be condemned.” (Matthew 12:33-37)

The Greek word that is translated give account is logos (logˊ-os), which means “something said,” and in this instance refers to a discourse or conversation (G3056). Jesus indicated that God’s moral accounting system is based on our speech, “for by your words you will be justified, and by your words you will be condemned” (Matthew 12:37). Justification means that you have a right standing before God. You are legally free from the guilt and the penalty of sin. “As a matter of right or justice: to absolve, acquit, clear from any charge or imputation” (G1344). John identified Jesus as “the Word,” logos, indicating that he is the moral standard by which our words will be judged.

Paul talked about God’s judgment in his letter to the Romans. Paul said, “For all who have sinned without the law will also perish without the law, and all who have sinned under the law will be judged by the law. For it is not the hearers of the law who are righteous before God, but the doers of the law who will be justified. For when the Gentiles, who do not have the law, by nature do what the law requires, they are a law to themselves, even though they do not have the law. They show that the work of the law is written on their hearts, while their conscience also bears witness, and their conflicting thoughts accuse or even excuse them on that day when, according to my gospel, God judges the secrets of men by Christ Jesus” (Romans 2:12-16). Paul indicated that the work of the law is written on the hearts of believers. In other words, the scriptures that reside in believers’ hearts cause them to do what the scriptures state.

Jesus said in his parable of the sower (Luke 8:5-8) that God’s word, or as Paul stated, his gospel, is sown like seed in people’s hearts. Jesus explained:

Now the parable is this: The seed is the word of God. The ones along the path are those who have heard; then the devil comes and takes away the word from their hearts, so that they may not believe and be saved. And the ones on the rock are those who, when they hear the word, receive it with joy. But these have no root; they believe for a while, and in time of testing fall away. And as for what fell among the thorns, they are those who hear, but as they go on their way they are choked by the cares and riches and pleasures of life, and their fruit does not mature. As for that in the good soil, they are those who, hearing the word, hold it fast in an honest and good heart, and bear fruit with patience. (Luke 8:11-15)

Jesus said God’s word must be held fast in our heart, or more specifically, lodged in our minds, for it to bear fruit. Another way of thinking about this is that we must first comprehend God’s word before it can be translated into action.

Paul argued that circumcision was of no value to the Jews if they did not obey God’s commandments. Paul said, “For circumcision indeed is of value if you obey the law, but if you break the law, your circumcision becomes uncircumcision. So, if a man who is uncircumcised keeps the precepts of the law, will not his uncircumcision be regarded as circumcision? Then he who is physically uncircumcised but keeps the law will condemn you who have the written code and circumcision break the law. For no one is a Jew who is merely one outwardly, nor is circumcision outward and physical. But a Jew is one inwardly, and circumcision is a matter of the heart by the Spirit, not by  the letter. His praise is not from man but from God. Being a Jew inwardly means that you are committed to living according to God’s word. This commitment is referred to as conversion and is our response to being regenerated by God or as Jesus put it, “born again” (John 3:3)

The book of Isaiah recounts God’s judgment of Israel and Judah and provides us with an example of how the whole world will be judged when Jesus returns. In Isaiah 29:13-16, the LORD said:

“Because this people draw near with their mouth
    and honor me with their lips,
    while their hearts are far from me,
and their fear of me is a commandment taught by men,
therefore, behold, I will again
    do wonderful things with this people,
    with wonder upon wonder;
and the wisdom of their wise men shall perish,
    and the discernment of their discerning men shall be hidden.”

Ah, you who hide deep from the Lord your counsel,
    whose deeds are in the dark,
    and who say, “Who sees us? Who knows us?”
You turn things upside down!
Shall the potter be regarded as the clay,
that the thing made should say of its maker,
    “He did not make me”;
or the thing formed say of him who formed it,
    “He has no understanding”?

God said the people had turned things upside down by denying him as their Creator, and in a very little while he intended to intervene (Isaiah 29:17).

Paul rebuked the Romans because of their unrepentant hearts and said, “You are storing up wrath for yourself on the day of wrath when God’s righteous judgment will be revealed” (Romans 2:5). Later in his letter, Paul talked about salvation being available to everyone and encouraged the Romans to confess their sin and be saved. Referring them back to Deuteronomy 30:1-14, where Moses talked about God circumcising the people’s hearts, Paul asked, “But what does it say? ‘The word is near you in your mouth and in your heart’ (that is, the word of faith that we proclaim); because if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For with the heart one believes and is justified, and with the mouth one confesses and is saved” (Romans 10:8-10).