Keep thy heart with all diligence; for out of it are the issues of life.

Proverbs 4:23

Physical fitness is important. But far more important than physical exercise and physical fitness is the spiritual aspect of our lives. And at the center of our spiritual fitness is the condition of our hearts.

Some have defined the heart as “the totality of man’s inner or immaterial nature.” Others have called the heart “the whole soul, or inner man” or “the center of all the issues of our life from a spiritual ethical point of view.” The heart sits at the very core of our being and makes us who we are.

When God created Adam and Eve, their hearts were right with God, and the result was that they glorified God and enjoyed communion with Him. Of course, Adam’s fall into sin changed all that: his clean heart became wicked, obdurate, rebellious, and impure.

From that corrupt stock comes a corrupt offspring. Jeremiah describes that corruption when he says, “the heart is deceitful above all things, and desperately wicked: who can know it?” (Jer. 17:9). With such a heart of stone, all we could do is rebel against God.

Thankfully, God has not left us in our fallen condition. By His grace, in Christ Jesus, God gives us new hearts, and He sprinkles clean water upon us in order to purify us from our spiritual uncleanness. He takes away our hearts of stone and gives us hearts of flesh. He puts His Spirit within us and causes us to walk in His statutes (cf. Ezek. 36:25-27).

But as long as we remain in this world our sanctification will not be complete, because our hearts, though renewed, are not completely renewed. Our old nature continues with us, thus involving us in a constant battle against sin. Therefore, God would have us, children redeemed by grace, to keep our hearts with all diligence.

Keeping our hearts involves guarding, watching, and preserving.

Imagine a military installation located in enemy territory. Such an installation would not last long if it were unguarded. An inattentive watchman amounts to an invitation for the enemy to attack. Such is the case with our hearts. We find ourselves in enemy territory, in which the devil constantly bombards us with lies about the “joys” and “rewards” of sin, while the world lures us to partake of its pleasures. To make matters worse, we have our old sinful flesh, the enemy within the gates.

Keeping our hearts is therefore of utmost importance.

Just as keeping a fortress involves constant and thorough examination of the surroundings in order to prevent enemy incursions, so does guarding the heart. If we truly want to keep the heart pure, we will seek to keep the enemy well out of striking distance. Practically, that means we will consider likely sources of temptations as well as specific ways to avoid them. If particular companions, reading material, television, or internet pose a danger to our hearts, we will take specific steps to safeguard ourselves.

In our pride, we sometimes imagine ourselves to be so strong that we would never fall into this or that sin. Keeping our hearts, we will assume the very opposite: given the right circumstances, and apart from God’s preserving grace, we are capable of committing any sin.

Keeping the heart involves not only examination of potential dangers but also eradication of present sin. The very presence of the enemy brings danger, even if that enemy happens to be a child spying out the camp. If we are serious about keeping the heart, we will take care not to allow even the smallest sin to remain in us. We will repent of every known sin, knowing that even the smallest sin endangers our spiritual well-being.

Keeping the heart, then, means giving deliberate attention to it in order to avoid all occasions of sin.

Keep thy heart with all diligence.

Literally, we could translate, “above all things that are to be watched, guard the heart.” More than anything else, guard the heart. Such is the seriousness of the spiritual battle we face.

We spend our time and money watching out for our homes, our cars, our retirement plans, our diet, and a host of other things. But none of these is more important than guarding the heart.

There never is a time when our hearts are free from danger. We must never imagine we have reached the point where guarding our hearts is unnecessary. The time we think that we are not subject to temptations is the moment the devil has already put his foot in the door.

Especially, we need to guard our hearts in seasons when we are likely to be tempted.

When we find ourselves in great prosperity, our temptation is to forget that we need God’s care and provision. Guarding our heart, we will remind ourselves that all our possessions come from God, who has entrusted them to us as stewards to use them for His glory.

When we are in adversity, the temptation is to forget that God’s loving-kindness will never depart from us. Guarding our heart, we will remember God’s care in the past and consider His promise to turn all things for our advantage. Furthermore, we will consider that our present sufferings are nothing compared with the glory to come.

When we are called to a particular duty toward God, it is easy to forget the importance of the work God has assigned to us. Guarding the heart means we will put our duties into proper perspective and strengthen ourselves in the Lord to seek first the Kingdom.

When Satan assails us with the promises of pleasure, we are liable to believe him. Guarding our hearts, we will reject the devil’s lies.

Guarding our heart means we will constantly go back to the truth of God’s Word. Psalm 119:11: “Thy word have I hid in mine heart, that I might not sin against thee.” There we learn the vanity of earthly things, and the value of the heavenly. In God’s Word we discover God’s faithfulness and the devil’s deceptions. Hebrews 4:12: “For the word of God is quick, and powerful, and sharper than any two-edged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart.” If, therefore, we desire to keep our hearts with all diligence, we will seek to become more familiar with the Scriptures, meditating upon them day and night.

Keeping the heart is not easy, by any stretch of the imagination; it is an exceedingly hard work. Indeed, it is an impossible work to perform in our own strength.

For that reason, guarding the heart includes our earnest prayers to God for grace. A military installation serving the king will not last long unless the king sends a constant supply of provisions and ammunition. Our hearts cannot be kept pure unless God gives us a constant supply of grace to preserve us from sin and to guide us in His ways. The fact that David prays, “Create in me a clean heart, O God; and renew a right spirit within me” (Ps. 51:10), shows his reliance upon God for grace.

The reason God would have us guard our hearts is that “out of it are the issues of life.”

Everything we experience in life is connected in some way to our hearts. “A good man out of the good treasure of the heart bringeth forth good things: and an evil man out of the evil treasure bringeth forth evil things” (Matt. 12:35). Guarding our hearts from idols, we will seek our happiness in God alone. Guarding our hearts from hatred and envy, we will also pursue the way of love and goodwill with our neighbor. Guarding our hearts from covetousness, we will instead seek the good of the Kingdom. Out of our hearts proceed the issues of life.

The two great issues of life, of course, are these: to glorify God and to enjoy Him forever. If we do not guard our hearts, we will not glorify God, nor will we enjoy fellowship with Him.

Of course, it is not the case that guarding our hearts earns the privilege of covenant fellowship with God. Rather, the idea is that God is pleased to give us the enjoyment of fellowship with Himself in the way of our keeping our hearts. When God desires to bless us with the enjoyment of Himself, He does so by first working in us so that we guard our hearts. Jesus Himself indicates this blessedness in His Sermon on the Mount, saying, “Blessed are the pure in heart: for they shall see God” (Matt. 5:8). We will experience the beginning of this blessedness in this life; but, especially, we shall enjoy covenant fellowship with God when we are taken to heaven.

More importantly, guarding our hearts is a means by which God brings glory to Himself. We ourselves will glorify God for the works He has worked in us. But others will also see good works flowing from a pure heart and give glory to God (cf. Matt. 5:16).

“Keep thy heart with all diligence, for out of it are the issues of life.”