Holiness, in its essence, is “apartness” or “separateness.” Purity of heart is definitely something that is different than the rest of the world, and is a primary aspect of this state of being set apart. When we are kept from disobedience, or sin, then we are in a state of apartness or being separate. Purity of heart then is a root, a foundation, of holiness.
In the sense being discussed here, the heart is the wellspring of who you are physically and ethically.
Proverbs 4:23-27 – Keep your heart with all vigilance, for from it flow the springs of life. Put away from you crooked speech, and put devious talk far from you. Let your eyes look directly forward, and your gaze be straight before you. Ponder the path of your feet; then all your ways will be sure. Do not swerve to the right or to the left; turn your foot away from evil.
When the heart is right, then our speech, our focus, and our walk will be in line and keep us from disobedience. How many times can you recall saying the wrong thing, or taking your eyes off of God, or walking where you shouldn’t be walking? My own personal list would be extensive.
According to this proverb, we need to keep our heart with all vigilance, for from it flow the springs of life. What is in our heart is what we express.
Luke 6:45 – The good person out of the good treasure of his heart produces good, and the evil person out of his evil treasure produces evil, for out of the abundance of the heart his mouth speaks.
What is in the abundance of your heart? You know it by the things you say. If your heart is pure, then your speech will be pure.
Additionally, the Bible tells us that the heart doesn’t just need to be pure, it needs to be continually purified. This is similar to the cleansing effect of fire on precious metals, refining them until they have no contrary elements left.
Psalm 66:10 – For you, O God, have tested us; you have tried us as silver is tried.
Proverbs 25:4 – Take away the dross from the silver, and the smith has material for a vessel;
Isaiah 48:10 – Behold, I have refined you, but not as silver; I have tried you in the furnace of affliction.
Daniel 12:10 – Many shall purify themselves and make themselves white and be refined, but the wicked shall act wickedly. And none of the wicked shall understand, but those who are wise shall understand.
Refinement is the state of being free from a mixture of false and true until only what is sincere and genuine remains. This is a process, not an instant occurrence. As you can tell from these passages, some of this refining takes place through affliction, some is self-induced by those who are wise. The implication is that if it is not done voluntarily, God can make it happen by outside means.
Another example of ongoing refinement is that it is like a vine that is pruned of dead, unproductive branches so that the plant has the energy and room to bear more fruit.
John 15:1-2 – “I am the true vine, and my Father is the vinedresser. Every branch in me that does not bear fruit he takes away, and every branch that does bear fruit he prunes, that it may bear more fruit.
1 John 3:6 – No one who abides in him keeps on sinning; no one who keeps on sinning has either seen him or known him.
3 John 1:11 – Beloved, do not imitate evil but imitate good. Whoever does good is from God; whoever does evil has not seen God.
Hebrews 12:14 – Strive for peace with everyone, and for the holiness without which no one will see the Lord.
Living in this way with a pure heart is what sets you apart from the rest of humanity; this is what holiness is.