“issues.” The word “issues” is not an exact translation, but it captures the sense of the text, and especially so because the Hebrew text is hard to literally translate here. The Hebrew word is totsaah (#08444 תּוֹצָאָה), and means a source, a border, an exit, an outgoing, extremity, or end. We think Bruce Waltke gets the sense correct, and writes: “The noun…designates the actions of the verb, the “goings out.” The cartographer uses it for the ‘exits’ of a city (Ezek. 48:30) and, by metonymy, for ‘borders,’ ‘extremities’ of a territory (1 Chron. 5:16); the rescued psalmist uses it for ‘escaping’ from/before death (Ps. 68:20). The point here is that the heart is the source of the bodies activities” (The New International Commentary on the Old Testament: The Book of Proverbs, William B. Eerdmans, Grand Rapids, MI, 2004).
Michael Fox writes that the Hebrew word means “outgoings,” and says, “In 20 of its 22 occurrences [totsaah] is a geographical term meaning ‘extremities,’ ‘outskirts,’ a sense inappropriate here. The verse designates the heart as the source of the ‘outgoings.’ Context requires understanding the word as the process or action of departure. In other words, life proceeds from the heart, which in this context is the inner core of the person’s life, not just what he is thinking at the time; the heart is life’s source” (M. Fox, The Anchor Bible: Proverbs).
Jesus confirmed that the heart is the source of much of what we say and do (Matt. 15:18-19; Mark 7:20-23), and because of that, we can easily see why the Word of God tells us to guard our hearts more closely than anything else we guard. The heart needs to be guarded because it is constantly changing—we cannot “get our hearts right” and then neglect them, thinking they will stay “right” forever.
The Bible has a lot to say about how a person’s heart can change. For example, it can turn directions (1 Kings 11:2-3, 9), become hard (Exod. 4:21; Josh. 11:20; Heb. 4:7); become proud or lifted up (Deut. 8:14; 2 Chron. 26:16; Ezek. 28:5); become humble (2 Chron. 32:26); become tender (2 Chron. 34:27); become strong (Ps. 10:17); become broken or be healed from being broken (Ps. 69:20; 147:3); be cleansed (Ps. 73:13); be destroyed (Ecc. 7:7); become “fat,” meaning stubborn (Isa. 6:10; Acts 28:27); be deceived (Isa. 44:20); become dull and stubborn (Matt. 13:15), be nourished (James 5:5); be established (James 5:8), be purified (James 4:8).
The great gatekeeper of the heart is the mind. Things get into our hearts through the mind, which is why it is so important to watch what we see and hear, and control our thoughts. Philippians 4:8 says to think about things that are true, pure, righteous, etc. Peace is also one of the guards that watches over our hearts (Phil. 4:7). It is also vital to control our actions. Uncontrolled actions only reinforce any anger or evil that is already in us. That is one reason why “self control” is one of the fruits of the spirit (Gal. 5:23).
The thoughts in our minds are constantly changing, which is why we use the phrase, “I changed my mind.” But the heart—the core of our mind and character—is more constant and changes much more slowly, and so it is a much better indicator of who we truly are as individuals. That is why the Bible says that God looks on the heart (1 Sam. 16:7), and why He tests our hearts (Ps. 7:9; 17:3; Jer. 11:20; 1 Thess. 2:4; Rev. 2:23). People who want to please God must take Proverbs 4:23 seriously, and work diligently to guard their hearts so that they become more and more pure before God.
There is a great war going on between God and Satan for people’s hearts. The Devil knows that if he can win people’s hearts they will suffer a lot in this life and the next. For Satan to win someone’s heart they don’t have to openly worship him; they just have to think and act in ungodly ways. If we do not control our thought life and our actions and bring them in line with the Word of God, our heart will change and we will slowly become more ungodly, and sadly, we will often not even be aware we are being more and more ungodly. Solomon was the wisest man on the earth at one time, but he gave in to his sensual desires and his heart changed. He ended his life with lots of money, with 1000 wives and concubines, and worshipping pagan gods (1 Kings 10:14-11:10), but Satan had won his heart and he “did evil in the eyes of Yahweh” (1 Kings 11:6). The blessing of God was off of his life. Wise Christians guard their heart and diligently watch what they see, hear, think, and do.