We must continue to remember the progression of the Beatitudes. We do not come now to a person who is pure in his own authority and power, rather, we come to someone who realized the impurity of his heart, cried out for forgiveness, and through Christ was heard. But even when we have come to understand our forgiveness, this should still be one of the most terrifying verses in all Scripture. "Blessed are the pure in heart, for they shall see God" (Matt. 5:8).
What is the heart of man? Christ is promising a blessing upon those who are pure in heart. In order to understand this, we must self-consciously reject the popular and modern understanding of "the heart." This is the understanding that the heart is the seat of the emotions and sentiments, as opposed to the intellectual part of man. To use the common spatial metaphor, the heart is supposed to be "deep down." This is in distinction to the rarefied atmosphere of the "head."
The biblical concept of the heart is quite different. In biblical terminology, the heart is the inside of a man -- and this includes all of his insides. The emotions, the will, the mind, etc. are all part of the inner man. This is in distinction to the externals, like the nose of man. And this particularly includes the externals of religious worship, like the prayers of man in front of others in the synagogue.
As Lloyd Jones put it, "According to the general scriptural usage of the term, the heart means the centre of the personality." It refers to what you are, in your innermost thoughts, choices, and motives, in the sight of God. The way you are on the inside will always reveal itself on the outside (somehow), but we must look where the Bible tells us to, not at traditions developed in the name of Scriptural authority.
Consider the teaching of Matthew 15:1-20: First, God commanded. Second, man substituted. Why do men do this? Their hearts are far from God. Of course, God sweeps all such chicanery away. Christ does not distinguish a man's heart from the dirt in his mind, but rather his heart from the dirt on his hands.
What then is true purity? According to Scripture, purity involves understanding the gospel (1 Pet. 1:22); obedience to scriptural authority, in an attitude of love (1 Tim. 1:3); singleness of purpose and mind (James 4:8); a display of wisdom from above which is first pure, then peaceable (James 3:17; Phil. 4:29); comfort of conscience (2 Tim. 1:3); freedom to enjoy God's creation (Titus 1:15); and hope of resurrection (1 John 3:3).
The pure are promised a vision of God. At the very first, we must remind ourselves of the greatness of this promise. Remember Moses, and his desire to see the glory of the Lord (read Exodus 33:12-23). First, God in His transcendence is invisible. In Col. 1:15, we are told that Christ is the image "of the invisible God." In 1 Tim. 1:17, Paul's benediction makes the same thing clear -- "Now to the King eternal, immortal, invisible, to God who alone is wise, be honor and glory forev forever and ever. Amen."
Will we ever see the invisible God with our eyes? No, we cannot."... who alone has immortality, dwelling in unapproachable light, whom no man has seen or can see, to whom be honor and everlasting power. Amen" (1 TIm. 6:16). However, the eye of faith is not constrained in the same way. Moses was commended for his faith at just this point. ". . . for he endured as seeing Him who is invisible" (Heb. 11:27).
But this does not mean that the physical eye is robbed of a vision of the glory of God. We shall see everything that can be seen, but we shall see it in Christ. We are not permitted to think that this restriction is a restriction. Again, in Colossians we see an image of an invisible God -- Christ. In Hebrews we are taught that Christ is the "brightness of His glory and the express image of his person . . . " (Heb. 1:3). Christ, the eternal Son of God, is eternally one with us. We will be with Him, and become like Him. And in seeing Him, we shall see the Father. "He who has seen Me has seen the Father . . . (John 14:9).