"Blessed are the pure in heart, for they shall see God" (Matt. 5:8).
The way you think determines the way you behave.
God is concerned about the way you think. That's why Paul said, "Do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what the will of God is, that which is good and acceptable and perfect" (Rom. 12:2). In Philippians 4:8 he instructs us to think about that which is true, honorable, right, pure, lovely, of good repute, excellent, and praiseworthy.
When Jesus spoke of a pure heart in Matthew 5:8, He was talking about sanctified thinking. The Greek word translated "heart" is kardia, from which we get the word cardiac. While we often relate heart to the emotions (e.g., "He has a broken heart"), the Bible relates it primarily to the intellect (e.g., "Out of the heart come evil thoughts, murders, adulteries, fornications, thefts, false witness, slanders"; Matt. 15:19). That's why you must "watch over your heart with all diligence" (Prov. 4:23).
In a secondary way, however, heart relates to the will and emotions because they are influenced by the intellect. If you are committed to something, it will affect your will, which in turn will affect your emotions.
The Greek word translated "pure" in Matthew 5:8 means "to cleanse." In the moral sense it speaks of being free from the filth of sin. It also refers to something that is unmixed, unalloyed, or unadulterated. Spiritual integrity and sincere motives are appropriate applications of its meaning to the Christian life.
Jesus was saying the kingdom citizen is blessed because he or she has pure thoughts and pure motives that together produce holy living. Someone might say he's religious and has pure motives, but if his behavior isn't righteous, his heart isn't fixed on God. Similarly, you can go to church, carry a Bible, and recite verses, but if your heart isn't clean, you haven't met God's standard.
You must do the will of God from a pure heart (Eph. 6:6). Toward that end, make David's prayer yours as well: "Create in me a clean heart, O God, and renew a steadfast spirit within me" (Ps. 51:10).
Suggestions for Prayer:
Memorize Psalm 19:14 and make it a part of your daily prayers.
For Further Study:
Read the following verses, noting the characteristics of a pure heart: Psalm 9:1, 26:2, 27:8, 28:7, and 57:7.
From Drawing Near by John MacArthur Copyright © 1993. Used by permission of Crossway Books, a division of Good News Publishers, Wheaton, IL 60187, www.crossway.com.